MATH203-19S1 Linear Algebra
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Final Exam
MATH203-19S1
Linear Algebra
1. Consider the matrix A = ┐ .
(a) Without performing any computations, explain why 0 is an eigenvalue of A. (b) Find the 0-eigenspace of A.
(c) Starting with x体 = ┌ ┐0(1) perform two iterations of the power method on A.
(d) Determine the domininant eigenvalue of A.
(e) Let v = ┌ ┐1(1) . Show that A is the matrix of the linear map projv : R2 → R2
(with respect to the standard basis on the domain and codomain).
(f) Let b| = ┌ ┐1(1) and b2 = ┌ 1┐ . What is the matrix of projv : R2 → R2 with
respect to the basis 夕 = (b|.b2 ) (on both domain and codomain)?
2. Consider the following vectors
┌ ┐1(1) ┌ ┐0(0) ┌ ┐2(0) ┌ 1(1) ┐
w| = '''0(0)'''. w2 = '''1(1)'''. w3 = '''1(1)'''. b = '''1''' .
We also define the subspace w = span{w|.w2.w3 扌
(a) In one sentence, explain why {w|.w2.w3 扌 is a basis for w .
(b) Use Gram-Schmidt to find an orthogonal basis for w .
(c) Find the projection of b onto w .
(d) Find a basis for w_ , the orthogonal complement of w .
(e) State an orthogonal basis for R4 that includes w| .
(f) Determine the Economy QR factorisation of the matrix B = ┌w| w2 w3 ┐ .
3. (a) Suppose M is an m ↓ ′ matrix of rank 亿 . What are the dimensions of the four fundamental subspaces of M?
(b) Give an example of an inner product on a vector space other than the dot product on R脯 .
(c) Let u = '(┌)1'(┐).v = '(┌)'(┐) and A = uvT .
i. Find |u|| , |v|| , |u|& , and |v|& .
ii. Find |A|| and |A|& .
(d) Give an example of a matrix A with condition number 62 (A) = 1.
4. Consider the matrices A = ┌0(1) |
1 1 |
1(0)┐ , B = AT A and C = AAT . |
(a) State the rank of A.
(b) Verify that u| = ┌ ┐1(1) and u2 = ┌ 1┐ are unit eigenvectors for C.
(c) Determine the singular values of A. (Hint: use (a) and (b)).
(d) Verify that v3 = '(┌)1'(┐) is a unit eigenvector for B .
(e) Determine the SVD of A, i.e., find a diagonal matrix Σ, and orthogonal matrices
U and v such that A = UΣvT .
(f) Determine the best rank 1 approximation to A.
2022-06-14