Diagonal theorem

Its two diagonals bisect each other. The required prove is stated below: The diagonals of a parallelogram are bisectors of each other. This implies that the diagonals divides each other into two equal parts. Comparing ΔABE and ΔDCE; AB = DC (given sides of the parallelogram) <ABC = <BDC (alternate angle property) <BAC = DCA (alternate angle ...

Diagonal theorem. First, we can use the Pythagorean Theorem to find the length of the second diagonal. 90 2 + 90 2 = d 2 8100 + 8100 = d 2 16200 = d 2 d = 127.3. This means that the diagonals are equal. If the diagonals are equal, the other two sides of the diamond are also 90 feet. Therefore, the baseball diamond is a parallelogram.

So, let us substitute the given values in the formula to get the unknown value, Length of body diagonal of a cube = √3a. ⇒ 8√3 = √3a. ⇒ a = 8. Therefore, the length of each side of the given cube = 8 units. Example 3: Find the length of the face diagonal of a cube when the side of the cube measures 6 units.

The hypotenuse is opposite the right angle and can be solved by using the Pythagorean theorem. In a right triangle with cathetus a and b and with hypotenuse c, Pythagoras' theorem states that: a² + b² = c². To solve for c, take the square root of both sides to get c = √(b²+a²). We can consider this extension of the Pythagorean theorem as ...Jun 2, 2020 · Draw a diagonal AC across the parallelogram, dividing it into two triangles ABD and BAC. By the alternate interior angle theorem, we know that the angles at A and C are congruent. Similarly, by the same logic, angles B and D are also congruent. AC, which is a side of both triangles, is obviously congruent to itself. To show why the diagonals of a rhombus are perpendicular, we can rotate the rhombus to look like a diamond and draw one diagonal as a horizontal line. Then, we can use the fact that the top and bottom triangles are congruent and isosceles to drop altitudes from the vertices to the horizontal diagonal. These altitudes form the other diagonal ...Rectangle Theorem #2: A rectangle has congruent diagonals. Example 3. Prove that if a quadrilateral has diagonals that bisect each other, then it is a parallelogram. This is the converse of parallelogram theorem #4 from Example C. Draw a quadrilateral with diagonals that bisect each other and preview the proof.In 1931, the Austrian logician Kurt Gödel published his incompleteness theorem, a result widely considered one of the greatest intellectual achievements of modern times. The theorem states that ...The diagonals of an isosceles trapezoid are also congruent, but they do NOT bisect each other. Isosceles Trapezoid Diagonals Theorem: The diagonals of an isosceles trapezoid are congruent. The midsegment (of a trapezoid) is a line segment that connects the midpoints of the non-parallel sides.

Theorem (2.2). Let f: X!Sbe a morphism of algebraic stacks that is quasi-separated and locally of approximation type. If fis separated (resp. has quasi-finite and separated diagonal), then H q n X=S is an algebraic stack with affine (resp. quasi-affine) diagonal. Theorem A is a consequence of Theorem (2.2) and the following two facts:4 Types Of Quadrilateral Shapes. 4.1 Properties of a Parallelogram. 5 Theorems of Quadrilateral Shapes. 5.1 1. If the diagonals of a quadrilateral bisect each other then it is a parallelogram. 5.2 2. If a pair of opposite side of a quadrilateral is parallel and congruent then the quadrilateral is a parallelogram. 5.3 3.Course: High school geometry > Unit 3. Proof: Opposite sides of a parallelogram. Proof: Diagonals of a parallelogram. Proof: Opposite angles of a parallelogram. Proof: The diagonals of a kite are perpendicular. Proof: Rhombus diagonals are perpendicular bisectors. Proof: Rhombus area. Prove parallelogram properties. Math >. The length of each diagonal is, according to Ptolemy's theorem, given by = + where a and b are the lengths of the parallel sides AD and BC, and c is the length of each leg AB and CD. The height is, according to the Pythagorean …Diagonally dominant matrix. In mathematics, a square matrix is said to be diagonally dominant if, for every row of the matrix, the magnitude of the diagonal entry in a row is larger than or equal to the sum of the magnitudes of all the other (non-diagonal) entries in that row. More precisely, the matrix A is diagonally dominant if. Parallelogram Diagonals Theorem Converse: If the diagonals of a quadrilateral bisect each other, then the figure is a parallelogram. 2. All the converses are true. 3. a) is a parallelogram because the opposite sides are parallel. b) Yes, the midpoint of the diagonals are the same, so they bisect each other. This corresponds with what we found ...You can derive this diagonal of square formula e.g., from calculating the Pythagorean theorem. As we noticed before, the diagonal of a square divides the square into two congruent right triangles. The legs are the sides of the square, and the length of the diagonal of the square is the hypotenuse.There are many important properties of determinants. Since many of these properties involve the row operations discussed in Chapter 1, we recall that definition now. We will now consider the effect …

Its two diagonals bisect each other. The required prove is stated below: The diagonals of a parallelogram are bisectors of each other. This implies that the diagonals divides each other into two equal parts. Comparing ΔABE and ΔDCE; AB = DC (given sides of the parallelogram) <ABC = <BDC (alternate angle property) <BAC = DCA (alternate angle ...The diagonal of a rectangle formula is derived using the Pythagoras theorem. Consider the rectangle given above. Let us consider a rectangle of length "l" and width "w". Let the length of each diagonal be "d". Applying Pythagoras theorem to the triangle BCD, d 2 = l 2 + w 2. Taking square root on both sides, d = √( l 2 + w 2)A linear pair of angles is always supplementary. This means that the sum of the angles of a linear pair is always 180 degrees. This is called the linear pair theorem. The linear pair theorem is widely used in geometry.The length of the diagonal of a square can be derived using the Pythagoras theorem. A diagonal of a square divides it into two right-angled triangles. Applying the Pythagoras theorem, we can find the length of the …

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We’ve underestimated the Pythagorean theorem all along. It’s not about triangles; it can apply to any shape.It’s not about a, b and c; it applies to any formula with a squared term.. It’s not about distance in the sense of walking diagonally across a room. It’s about any distance, like the “distance” between our movie preferences or colors.There are also special cases of right triangles, such as the 30° 60° 90, 45° 45° 90°, and 3 4 5 right triangles that facilitate calculations. Where a and b are two sides of a triangle, and c is the hypotenuse, the Pythagorean theorem can be written as: a 2 + b 2 = c 2. EX: Given a = 3, c = 5, find b: 3 2 + b 2 = 5 2 9 + b 2 = 25 b 2 = 16 b = 4, Diagonal bisect each other. Now, In ΔAOB and ΔCOB, OB = OB (Given) AO = CO (diagonals are bisected) AB = CB (Sides of the square) ... Thus by mid point theorem, SR || AC and SR = ½ AC (ii) In ΔBAC, P is the mid point of AB and Q is the mid point of BC. Thus by mid point theorem, PQ || AC and PQ = ½ ACThis is one of the most important theorems in this textbook. We will append two more criteria in Section 5.1. Theorem 3.6.1: Invertible Matrix Theorem. Let A be an n × n matrix, and let T: Rn → Rn be the matrix transformation T(x) = Ax. The following statements are equivalent:

This famous paper by George Cantor is the first published proof of the so-called diagonal argument, which first appeared in the journal of the German ...A parallelogram is an example of quadrilaterals that have opposite sides to be equal. Its two diagonals bisect each other.. The required prove is stated below:. The diagonals of a parallelogram are bisectors of each other. This implies that the diagonals divides each other into two equal parts.. Comparing ΔABE and ΔDCE; AB = DC (given sides of the parallelogram)Ptolemy's theorem. Ptolemy's theorem is a relation among these lengths in a cyclic quadrilateral. In Euclidean geometry, Ptolemy's theorem is a relation between the four sides and two diagonals of a cyclic quadrilateral (a quadrilateral whose vertices lie on a common circle). The theorem is named after the Greek astronomer and mathematician ... A diagonal divides the square into two equal right-angled triangles. The diagonal is the hypotenuse of each triangle. In fact, each diagonal divides the square into two congruent isosceles right triangles, with two vertices of 45°, as the vertical divides the square’s right angles in half. Pythagorean Theoremif one of the axis coincides with the axis of symmetry, the tensor of inertia has a simple diagonal form. For an axisymmetric body, the moments of inertia about the two axis in the plane will be equal. Therefore, the moment about any axis in this plane is equal to one of these. And therefore, any axis in the plane is a principal axis.symmetric matrix are real, Theorem 8.2.2 is also called the real spectral theorem, and the set of distinct eigenvalues is called the spectrum of the matrix. In full generality, the spectral theorem is a similar result for matrices with complex entries (Theorem 8.7.8). Example 8.2.4 Find an orthogonal matrix P such that P−1AP is diagonal, where A= A diagonal divides the square into two equal right-angled triangles. The diagonal is the hypotenuse of each triangle. In fact, each diagonal divides the square into two congruent isosceles right triangles, with two vertices of 45°, as the vertical divides the square’s right angles in half. Pythagorean TheoremThe advantage of the inclusive definition is that any theorem proved for trapezoids is automatically a theorem about parallelograms. This fits best with the nature of twentieth-century mathematics. It is possible to function perfectly well with either definition.The properties of isosceles trapezoids are defined by the following theorems: Theorem: Both pairs of base angles of an isosceles trapezoid are congruent. The converse can also be used: If a trapezoid has congruent base angles, then it is an isosceles trapezoid. Theorem: The diagonals of an isosceles trapezoid are congruent.The length of a diagonal, 'd' of a square with side length 'a' is calculated using the Pythagoras theorem. Observe the following square to see that the length ...

Jul 18, 2012 · Theorem: The diagonal through the vertex angles is the angle bisector for both angles. The proof of this theorem is very similar to the proof above for the first theorem. If we draw in the other diagonal in K I T E we find that the two diagonals are perpendicular. Kite Diagonals Theorem: The diagonals of a kite are perpendicular.

A diagonal of a rectangle cuts the rectangle into 2 right triangles with sides equal to the sides of the rectangle and with a hypotenuse that is the diagonal. All you need to do is use the pythagorean theorem:Converse of Theorem 3: If the diagonals in a quadrilateral bisect each other, then it is a parallelogram. In the quadrilateral PQTR, if PE=ET and ER=EQ, then it is a parallelogram. Given: The diagonals PT and QR bisect each other. To Prove: PQRT is a parallelogram. Proof: Suppose that the diagonals PT and QR bisect each other. Compare triangle ...5 Haz 2017 ... Parallelogram Theorem #1: Each diagonal of a parallelogram divides the parallelogram into two congruent triangles. Parallelogram Theorem #2: The ...The hypotenuse is opposite the right angle and can be solved by using the Pythagorean theorem. In a right triangle with cathetus a and b and with hypotenuse c, Pythagoras' theorem states that: a² + b² = c². To solve for c, take the square root of both sides to get c = √(b²+a²). We can consider this extension of the Pythagorean theorem as ...Diagonal length of a square with each side a units = a$\sqrt{2}$ units. Length of Diagonal of Rectangle. A diagonal of a rectangle divides it into two right-angled triangles. Applying the Pythagoras theorem, we can find the length of diagonal of a rectangle with length (l) and breadth (b) as. d$^{2}$ = l$^{2}$ + b$^{2}$Lesson 6: Theorems concerning quadrilateral properties. Proof: Opposite sides of a parallelogram. Proof: Diagonals of a parallelogram. Proof: Opposite angles of a parallelogram. Proof: The diagonals of a kite are perpendicular. Proof: Rhombus diagonals are perpendicular bisectors. Proof: Rhombus area.theorem it is given in the converse. Thus, Theorem 8.2 can be stated as given below : If a quadrilateral is a parallelogram, then each pair of its opposite sides is equal. So its converse is : Theorem 8.3 : If each pair of opposite sides of a quadrilateral is equal, then it is a parallelogram. Can you reason out why?Lateral edge: Since we've calculated the base diagonal, let's now use it to count the length of the lateral edge, d. To do this, observe that it forms a right triangle with the pyramid's height and half of the base diagonal. Therefore, the Pythagoras theorem comes in handy again: d² = H² + (diagonal / 2)² = 12² + 5² = 169, which gives d ...While one method of proof will be shown, other methods are also possible. Definition and Theorems pertaining to a rectangle: DEFINITION: A rectangle is a parallelogram with four right angles. THEOREM: If a parallelogram is a rectangle, it has congruent diagonals. *. THEOREM Converse: If a parallelogram has congruent diagonals, it is a rectangle.

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28 Mar 2009 ... An illustration of Cantor's diagonal argument for the existence of uncountable sets. The sequence at the bottom cannot occur anywhere in the ...Each diagonal acts as the hypotenuse for the right triangles so formed. Applying Pythagoras theorem to the triangle so formed, d 2 = l 2 + w 2, where d is diagonal, l is length and w is the width of the rectangle. Taking square root on both sides, √(d 2) = √( l 2 + w 2). Thus, the diagonal of a rectangle formula is: √( l 2 + w 2).Hence, the diagonals of an isosceles trapezoid are congruent. Property of trapezoid related to the length of diagonals Theorem 3: In a trapezoid, the midsegment is parallel to the bases, and the length of the midsegment is half the sum of the lengths of the bases.Parallelogram Diagonals Theorem Converse: If the diagonals of a quadrilateral bisect each other, then the figure is a parallelogram. If then . 4. Parallel Congruent Sides Theorem: If a quadrilateral has one set of parallel lines that are also congruent, then it is a parallelogram. If then1 Answer. Goedel provides a way of representing both mathematical formulas and finite sequences of mathematical formulas each as a single positive integer (by replacing each symbol with a number, and then using the numbers as exponents in the prime factorization).However, from Theorem 4.5, if all diagonal entries of a sign stable pattern A are negative and if B = − D, then C is also sign stable, which is an example for which both A and C require a unique refined inertia. See, e.g., [13] for results on sign patterns requiring unique refined inertia.In future sections, we will see that using the following properties can greatly assist in finding determinants. This section will use the theorems as motivation to provide various examples of the usefulness of the properties. The first theorem explains the affect on the determinant of a matrix when two rows are switched.Jan 21, 2021 · Cantor's theorem implies that no two of the sets. $$2^A,2^ {2^A},2^ {2^ {2^A}},\dots,$$. are equipotent. In this way one obtains infinitely many distinct cardinal numbers (cf. Cardinal number ). Cantor's theorem also implies that the set of all sets does not exist. This means that one must not include among the axioms of set theory the ... ….

The diagonal of a rectangle formula is derived using the Pythagoras theorem. Consider the rectangle given above. Let us consider a rectangle of length "l" and width "w". Let the length of each diagonal be "d". Applying Pythagoras theorem to the triangle BCD, d 2 = l 2 + w 2. Taking square root on both sides, d = √( l 2 + w 2)if one of the axis coincides with the axis of symmetry, the tensor of inertia has a simple diagonal form. For an axisymmetric body, the moments of inertia about the two axis in the plane will be equal. Therefore, the moment about any axis in this plane is equal to one of these. And therefore, any axis in the plane is a principal axis.A diagonal line is a line segment that connects the two vertices of a shape, which are not already joined by an edge. It does not go straight up, down or across. The shape of the diagonals is always a straight line. In other words, a diagonal is a straight line that connects the opposite corners of a polygon or a polyhedron, through its vertex.11 Oca 2023 ... Diagonal of a cube formula. For a cube, we find the diagonal by using a three-dimensional version of the Pythagorean Theorem/distance formula ...In Euclidean geometry, a cyclic quadrilateral or inscribed quadrilateral is a quadrilateral whose vertices all lie on a single circle. This circle is called the circumcircle or circumscribed circle, and the vertices are said to be concyclic. The center of the circle and its radius are called the circumcenter and the circumradius respectively.Also, the diagonal that connects the common vertices of the pairs of adjacent sides bisects the other diagonal, making the midpoint of . Therefore, . By the 30-60-90 Theorem, since and are the short and long legs of , By the 45-45-90 Theorem, since and are the legs of a 45-45-90 Theorem, . The diagonal has length .For the first idea, use the Pythagorean Theorem: , where a and b are the side lengths of the square and c is the length of the diagonal. 2. If you know that ALL squares can be made into two special right triangles such that their angles are 45-45-90, then there's a formula you could use: In mathematics, the simplest form of the parallelogram law (also called the parallelogram identity) belongs to elementary geometry. It states that the sum of the squares of the lengths of the four sides of a parallelogram equals the sum of the squares of the lengths of the two diagonals. We use these notations for the sides: AB, BC, CD, DA. The diagonal of a cube formula helps in measuring the diagonals of a cube. Since a cube has two kinds of diagonals, there are 2 different formulas for calculating their value. Face … Diagonal theorem, The diagonal form for diagonalizable matrices, for instance normal matrices, is a special case of the Jordan normal form. [6] [7] [8] The Jordan normal form is named after Camille Jordan , who first stated the Jordan decomposition theorem in 1870., Let L, W, and H represent the dimensions (length, width, and height) of a rectangular prism, let C represent a diagonal of the bottom face, and let D represent a long diagonal of the prism. We use the regular (2-dimensional) Pythagorean theorem on two right triangles. One right triangle has legs L & W and hypotenuse C. This gives …, Here’s how this theorem applies to squaring a foundation. Say you are laying the foundation of a square room with 10-foot long walls on each side. Think of the room as two separate right triangles. The diagonal that cuts across the room, and which forms the hypotenuse of the triangles, should be 14.142 feet: 102+102=200., To show why the diagonals of a rhombus are perpendicular, we can rotate the rhombus to look like a diamond and draw one diagonal as a horizontal line. Then, we can use the fact that the top and bottom triangles are congruent and isosceles to drop altitudes from the vertices to the horizontal diagonal. These altitudes form the other diagonal ..., Turing's proof is a proof by Alan Turing, first published in January 1937 with the title "On Computable Numbers, with an Application to the Entscheidungsproblem".It was the second proof (after Church's theorem) of the negation of Hilbert's Entscheidungsproblem; that is, the conjecture that some purely mathematical yes–no questions can never be answered …, Since the diagonals of a rhombus bisect each other at right angles, therefore, we have a right-angled triangle where two sides are known and we can find the third side using the Pythagoras theorem. Half of the unknown diagonal = √(25 2 - 20 2) = √(625 - 400) = √225 = 15 units. Since this is half the diagonal, the full length of the ..., Advertisement When you look at an object high in the sky (near Zenith), the eyepiece is facing down toward the ground. If you looked through the eyepiece directly, your neck would be bent at an uncomfortable angle. So, a 45-degree mirror ca..., The diagonal of a rectangle divides the rectangle into two congruent right triangles. Hence, the diagonal can be found using Pythagoras theorem. Where, diagonal acts as hypotenuse, sides are considered as the base and perpendicular. The formula to find the diagonal of a rectangle is: Diagonal = √(l 2 + b 2) Here, l = Length of the rectangle, The present entry surveys the two incompleteness theorems and various issues surrounding them. (See also the entry on Kurt Gödel for a discussion of the …, A generalized form of the diagonal argument was used by Cantor to prove Cantor's theorem: for every set S, the power set of S—that is, the set of all subsets of S (here written as P(S))—cannot be in bijection with S itself. This proof proceeds as follows: Let f be any function from S to P(S). It suffices to prove f cannot be surjective., Figure 1.6. 2. This is the Pythagorean Theorem with the vertical and horizontal differences between (x_1, y_1) and (x_2, y_2). Taking the square root of both sides will solve the right hand side for d, the distance. ( x 1 − x 2) 2 + ( y 1 − y 2) 2 = d. This is the Distance Formula. The following problems show how to apply the distance formula., A diagonal divides the square into two equal right-angled triangles. The diagonal is the hypotenuse of each triangle. In fact, each diagonal divides the square into two congruent isosceles right triangles, with two vertices of 45°, as the vertical divides the square’s right angles in half. Pythagorean Theorem, In mathematics, the simplest form of the parallelogram law (also called the parallelogram identity) belongs to elementary geometry. It states that the sum of the squares of the lengths of the four sides of a parallelogram equals the sum of the squares of the lengths of the two diagonals. We use these notations for the sides: AB, BC, CD, DA., Theorem 5.2.1 5.2. 1: Eigenvalues are Roots of the Characteristic Polynomial. Let A A be an n × n n × n matrix, and let f(λ) = det(A − λIn) f ( λ) = det ( A − λ I n) be its characteristic polynomial. Then a number λ0 λ 0 is an eigenvalue of A A if and only if f(λ0) = 0 f ( λ 0) = 0. Proof., What do these arguments have in common - what makes an argument a diagonal argument? And why do some diagonal arguments lead to theorems, while others lead to ..., So, let us substitute the given values in the formula to get the unknown value, Length of body diagonal of a cube = √3a. ⇒ 8√3 = √3a. ⇒ a = 8. Therefore, the length of each side of the given cube = 8 units. Example 3: Find the length of the face diagonal of a cube when the side of the cube measures 6 units., Cantor shocked the world by showing that the real numbers are not countable… there are “more” of them than the integers! His proof was an ingenious use of a proof by contradiction. In fact, he could show that there exists infinities of many different “sizes”! , a quadrilateral with four right angles. Theorem 6.3A. If a quadrilateral is a rectangle, then it is a parallelogram. (Rect. → ) Theorem 6.3B. If a parallelogram is a rectangle, then its diagonals are congruent. Rect. → ≅ diagonals) Theorem 6.3C. If one angle of a parallelogram is a right angle, then the parallelogram is a rectangle ( with ..., Parallelogram Diagonals Theorem Converse: If the diagonals of a quadrilateral bisect each other, then the figure is a parallelogram. 2. All the converses are true. 3. a) is a parallelogram because the opposite sides are parallel. b) Yes, the midpoint of the diagonals are the same, so they bisect each other. This corresponds with what we found ..., ... theorem using the diagonal argument. keywords: Cantor-Schröder-Bernstein theorem, diagonal argument, infinite sets The most updated version of this white ..., 7. No such matrix by spectral theorem. Spectral theorem tells us a symmetric matrix is diagonalizable, but this would mean that the geometric multiplicities need to equal the algebraic multiplicities for all eigenvalues, in order to add up to 2. 8. 0 0 ˇ 0 . B. The proof of the spectral theorem. Part I., Theorem (2.2). Let f: X!Sbe a morphism of algebraic stacks that is quasi-separated and locally of approximation type. If fis separated (resp. has quasi-finite and separated diagonal), then H q n X=S is an algebraic stack with affine (resp. quasi-affine) diagonal. Theorem A is a consequence of Theorem (2.2) and the following two facts:, Then use the Pythagorean Theorem, d = √(l² + w²), to calculate the diagonal of the rectangle. Example 1: Find the diagonal of a rectangle with perimeter 26 cm ..., Chebyshev’s theorem, or inequality, states that for any given data sample, the proportion of observations is at least (1-(1/k2)), where k equals the “within number” divided by the standard deviation. For this to work, k must equal at least ..., If , , and represent the lengths of the side, the short diagonal, and the long diagonal respectively, then the lengths of the sides of are , , and ; the diagonals of are and , respectively. Now, Ptolemy's theorem states that , which is equivalent to upon division by . 1991 AIME Problems/Problem 14. A hexagon is inscribed in a circle., Draw the diagonal of the square in the figure: Figure \(\PageIndex{3}\) Notice that the diagonal of the square is also the diameter of the circle. Define variables: Let \(c= \text{ …, An arbitrary quadrilateral and its diagonals. Bases of similar triangles are parallel to the blue diagonal. Ditto for the red diagonal. The base pairs form a parallelogram with half the area of the quadrilateral, A q, as the sum of the areas of the four large triangles, A l is 2 A q (each of the two pairs reconstructs the quadrilateral) while that of the small triangles, A s is a …, A bijective function, f: X → Y, from set X to set Y demonstrates that the sets have the same cardinality, in this case equal to the cardinal number 4. Aleph-null, the smallest infinite cardinal. In mathematics, a cardinal number, or cardinal for short, is what is commonly called the number of elements of a set.In the case of a finite set, its cardinal number, or …, Also, the diagonal that connects the common vertices of the pairs of adjacent sides bisects the other diagonal, making the midpoint of . Therefore, . By the 30-60-90 Theorem, since and are the short and long legs of , By the 45-45-90 Theorem, since and are the legs of a 45-45-90 Theorem, . The diagonal has length ., Theorem 1.4. Every polygon has a triangulation. Proof. We prove this by induction on the number of vertices n of the polygon P.Ifn= 3, then P is a triangle and we are finished. Let n > 3 and assume the theorem is true for all polygons with fewer than n vertices. Using Lemma 1.3, find a diagonal cutting P into polygons P 1 and P 2. Because ..., A generalized form of the diagonal argument was used by Cantor to prove Cantor's theorem: for every set S, the power set of S—that is, the set of all subsets of S (here written as P(S))—cannot be in bijection with S itself. This proof proceeds as follows: Let f be any function from S to P(S). It suffices to prove f … See more, The correct answer is 150. Simply add the three known angles together and subtract that from 360, because all the angles in a quadrilateral add up to 360. The reason your method won't work …, Diagonal matrices have a very simple multiplicative structure; when one multiplies two diagonal matrices, the entries in both main diagonals multiply termwise. In particular, one can see why a diagonal matrix should satisfy its own characteristic polynomial: each entry on the main diagonal is an eigenvalue of the matrix.