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Q2E

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Linear Algebra With Applications
Found in: Page 1
Linear Algebra With Applications

Linear Algebra With Applications

Book edition 5th
Author(s) Otto Bretscher
Pages 442 pages
ISBN 9780321796974

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Short Answer

Let be an orthogonal 2X2 matrix. Use the image of the unit circle to find the singular values of A.

The singular values of A are σ1=1and σ2=1are derived using the theorem 8.3.2

See the step by step solution

Step by Step Solution

Step 1 of 2: Given information

It is given that A is an orthogonal 2x2 matrix.

Step 2 of 2: Find the singular value

Let us have v1=10 and v2=01, where v1,v2 forms an orthonormal basis of .

Here, the unit circle consists of the vectors of the form x=costv1+sintv1 and the image of the unit circle consists of the vectors of the form

Lx=costLv1+sintLv2

Therefore, the image is the ellipse whose semi-major and semi-minor axes are Lv1 and Lv2 and respectively.

The length of the axes are Lv12=Av1xAv1=v1TATAv1

, =v1Tl2v1,where A is an orthogonal matrix =v1Tv1=1as v1 is an unit vector Lv22=Av2xAv2=v1TATAv2,=v1Tl2v1where A is an orthogonal matrix =v1Tv1=1as v2 is an unit vector

Thus Lv22=1,Lv22=1

Thus, the singular values of A are σ1=1 and σ2=1.

Result: The singular values of A are σ1=1 and σ2=1

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