CAP 1 Flashcards
What is a matrix?
A matrix is an array of elements set out in a pair of brackets.
How many rows and columns does a MxN matrix have?
M rows and N columns
What is a square matrix
A matrix that has the same number of rows as columns
What is an identity matrix?
A matrix with 1s in the leading diagonals with all other elements as 0
What must be true for matrices to be added or subtracted?
The matrices must have the same dimensions.
What is a scalar?
A dimensional quantity - a number
What law is A * (B * C) = (A * B) * C ?
The associative law
What law is A * B = B * A
The commutative law
Is matrix addition associative/commutative?
Yes, both
Is matrix subtraction associative/commutative?
No. neither
Is matrix multiplication commutative?
Not in general
The composite matrix ABCD should be multiplied from…
… right to left
A(B(C(D)))
What point always maps onto itself after a linear transformation?
The origin
(k 0)
0 k
An enlargements by scale factor k
(k 0)
0 1
Stretch scale factor k parallel to X axis
(1 0)
0 k
Stretch scale factor k parallel to Y axis
Rotation, anticlockwise by θ
(cos θ - sin θ)
sin θ cos θ
G followed by H is …
H x G
P followed by Q is …
Q x P
(1 k)
0 1
A shear, x - axis fixed, with (0,1) mapped to (k,1)
(1 0)
k 1
A shear, y - axis fixed, with (1,0) mapped to (1,k)
A shear maintains…
area
Invariant points are…
points which map to themselves
How do you find points that are invariant under a transformation:
(a b)
(c d)
(a b) x (x) = (x)
c d) x (y) = (y