Question

Points A and B are at `(9 ,2 )` and `(3 ,8 )`, respectively. Point A is rotated counterclockwise about the origin by `pi/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?

Answer 1

`C=(-7,10)`

Explanation:

`"under a counterclockwise rotation about the origin of "pi/2`

`• " a point "(x,y)to(-y,x)`

`rArrA(9,2)toA'(-2,9)"where A' is the image of A"`

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

`rArrulb-ulc=2(ula'-ulc)`

`rArrulb-ulc=2ula'-2ulc`

`rArrulc=2ula'-ulb`

`color(white)(rArrulc)=2((-2),(9))-((3),(8))`

`color(white)(rArrulc)=((-4),(18))-((3),(8))=((-7),(10))`

`rArrC=(-7,10)`