Question 1
1.1 State whether each of the following statements is true or false. Justf:f'y yov.r answer.
a) If a, b and c are any three vectors in JR3; , then a• (b + c) = a x b + a x c.
[2]
b) j x i = k.
[3]
c) If AB and BA are both defined, then A and B are square matrices.
[3]
d) If matrix A has a column of all zeros, then so does AB if this product is defined. [3]
e) The expressions tr(AT A) and tr(AAT) are defined for every matrix A.
[2]
f) The sum of two diagonal matrices of the same size is also a diagonal matrix.
[3]
1.2 Given that u = ni + 5j - v'7kand iul = 9, find the possihle values of the scalar O'..
[4]
1.3 Determine the area of parallelogram whose adjacents sides are a = 2i - 4j + 5k and b =
i - 2j - 3k. Leave your answer iu surd form.
[5]
Question 2
2.1 Write down a 4 x 4 matrix whose if" entry is given by aij = ij~l , and comment on your
matrix.
[6]
2.2 Let A be a square matrix. State what is meant by each of the following statements.
a) A is symmetric
[2]
b) A is orthogonal
[2]
c) A is skew-symmetric
[2]
2.3 Consider the following matrices.
~), 1 -?
A= 4 2
B= (
( 0 1 -2
-2
~l),and D=
2
(21
2
1
3)_
4
a) Given that C = AB, determine the element c32 .
[4]
b) Find (3Af.
[3]
c) Is DB defined? If yes, then find it, au<l hence calculate tr(DB).
[6]
2.4 Suppose A is a square matrix. Check if the matrix B = 3(A - AT) is skew-symmetric? [5]
1