Homework # 9 - Math 241
The problems on this homework must be done alone. The honor code is in effect.
First name: Last name:
1. Let \(\left[\begin{array}{cc} 1 & 1 \\ 0 & 1\end{array}\right]\). Is \(A\) diagonalizable?
a. Yes.
b. No, because it has too few eigenvalues.
c. No, because there aren't two linearly independent eigenvectors.
2. Let \(\left[\begin{array}{cc} 1 & 0 \\ 0 & 1\end{array}\right]\). Is \(A\) diagonalizable?
3. Say \(T:{\bf R}^2 \rightarrow {\bf R}^2\) is the linear transformation which reflects the plane over some line through the origin (you don't need to know which line, and you don't need to know the 2 by 2 matrix \(A\) such that \(T(\vec{x}) = A\vec{x}\)). What are the eigenvalues of T (Just think about it)?
a. There are none
b. Only 1
c. Only -1
d. 1 and -1
c. 1 and 0
4. Say \(T:{\bf R}^2 \rightarrow {\bf R}^2\) is the linear transformation which rotates the plane by 45 degrees around the origin. What are the eigenvalues of T (Just think about it)?
5. Say \(T:{\bf R}^2 \rightarrow {\bf R}^2\) is the linear transformation which rotates the plane by 180 degrees around the origin. What are the eigenvalues of T (Just think about it)?
d. 0 and 1
6. Say \(T:{\bf R}^3 \rightarrow {\bf R}^3\) is the linear transformation which rotates three dimensional space by 45 degrees around some line through the origin. What are the eigenvalues of T (Just think about it)?
7. Consider the triangle with vertices A(1,2,3), B(5,5,3), and C(3,4,4). Find cos\(\theta\) where \(\theta\) is the smallest angle in the triangle.
a. -14/15
b. -1/15
c. 0
d. 1/15
e. 14/15