Question

ΔABC is translated 2 units down and 1 unit left. Then it is rotated 90° clockwise about the origin to create ΔA′B′C′. What are the coordinates of the vertices of ΔA′B′C′ ?

Answer 1

so start off by writing out the vertices
we can define this transformation

the first transformation is the
mapping:
(x,y) -> ( x - 1 , y - 2 )

then the rotation transformation 90 degrees clockwise is the mapping :
(u,v) -> (v, -u )