Question

A triangle has vertices (–2, –3), (3, 5), and (8, –1).

b. Write a matrix expression to represent rotating the triangle 90° clockwise. Evaluate the matrix expression and list the coordinates of the vertices of the transformed figure.

Answer 1

(1,    0)
 0     -1

Explanation
Draw a unit squares with vertices I(1,0), J(1,1), and K(0,1)
Take any point, say I(1,0) and rotate through 90 degrees. The new co-ordinates become (0,-1)
This forms the matrix of transformation.
Then premultiply the matrix with co-ordinates given above:
This gives
(-3,2), (5,-3), (-1, -8)