Exam 3 Problems - Matrices and Matrix Calculations | M 340L, Exams of Mathematics

Material Type: Exam; Professor: Schurle; Class: MATRICES/MATRIX CALCULATNS-C S; Subject: Mathematics; University: University of Texas - Austin; Term: Fall 2010;

Typology: Exams

Pre 2010

Uploaded on 05/23/2010

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M340L EXAM 3B 9:00
FALL, 2009
Dr. Schurle
Your name:
Your UTEID:
Show all your work on these pages. Be organized and neat. Your work should be your
own; there should be no talking, reading notes, checking laptops, using cellphones, .. . .
1. (10 points) Explain in detail why two vectors uand vin Rpare orthogonal exactly
when ||u+v||2=||u||2+||v||2.
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M340L EXAM 3B 9:

FALL, 2009

Dr. Schurle

Your name:

Your UTEID:

Show all your work on these pages. Be organized and neat. Your work should be your own; there should be no talking, reading notes, checking laptops, using cellphones,....

  1. (10 points) Explain in detail why two vectors u and v in Rp^ are orthogonal exactly when ||u + v||^2 = ||u||^2 + ||v||^2.

YOUR SCORE: /

  1. (10 points) Using only algebra and definitions, show why eigenvectors v 1 and v 2 cor- responding to eigenvalues 3 and 5, respectively, for some matrix A must be linearly independent.
  2. (10 points) Is 4 an eigenvalue of the matrix

  

  ? If so, find a basis for its

eigenspace. If not, justify your answer.

  1. Let V be a vector space with basis B = {b 1 , b 2 }. Suppose that T : V → R^3 is a linear transformation such that

T (b 1 ) =

 

  and T (b 2 ) =

 

 

(a) (6 points) Calculate and simplify T (4b 1 − 2 b 2 ).

(b) (6 points) What is the matrix for T relative to the basis B and the standard basis for R^3?

(c) (6 points) Suppose C is another basis for V , where

c 1 = 5b 1 + 2b 2 ,

c 2 = 7b 1 + 3b 2. What is the matrix for T relative to the basis C and the standard basis for R^3?

  1. Let W be the subspace of R^4 spanned by the vectors u 1 , u 2 , u 3 , where

u 1 =

  

   , u 2 =

  

   , u 3 =

  

  .

(a) (4 points) Verify that {u 1 , u 2 , u 3 } is an orthogonal basis for W.

(b) (10 pts.) Write y =

  

   as the sum of a vector in W and a vector in W ⊥.

(c) (4 points) Find the distance from y to the subspace W.

(d) (6 points) Find a basis for W ⊥.