Points A and B are at (9 ,4 ) and (7 ,2 ), respectively. Point A is rotated counterclockwise about the origin by (3pi)/2 and dilated about point C by a factor of 2 . If point A is now at point B, what are the coordinates of point C?

1 Answer
May 26, 2018

C=(1,-20)

Explanation:

"under a counterclockwise rotation about the origin of "(3pi)/2

• " a point "(x,y)to(y,-x)

A(9,4)toA'(4,-9)" where A' is the image of A"

vec(CB)=color(red)(2)vec(CA')

ulb-ulc=2(ula'-ulc)

ulb-ulc=2ula'-2ulc

ulc=2ula'-ulb

color(white)(ulc)=2((4),(-9))-((7),(2))

color(white)(ulc)=((8),(-18))-((7),(2))=((1),(-20))

C=(1,-20)