Question

Points A and B are at `(1 ,7 )` and `(3 ,9 )`, respectively. Point A is rotated counterclockwise about the origin by `(3pi)/2` and dilated about point C by a factor of `4`. If point A is now at point B, what are the coordinates of point C?

Answer 1

`C=(25/3,-13/3)`

Explanation:

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

`• " a point "(x,y)to(y,-x)`

`A(1,7)toA'(7,-1)" where A' is the image of A"`

`vec(CB)=color(red)(4)vec(CA')`

`ulb-ulc=4(ula'-ulc)`

`ulb-ulc=4ula'-4ulc`

`3ulc=4ula'-ulb`

`color(white)(3ulc)=4((7),(-1))-((3),(9))`

`color(white)(3ulc)=((28),(-4))-((3),(9))=((25),(-13))`

`ulc=1/3((25),(-13))=((25/3),(-13/3))`

`rArrC=(25/3,-13/3)`