Question

Points A and B are at `(4 ,1 )` and `(5 ,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=(-1/3,-25/3)`

Explanation:

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

`• " a point "(x,y)to(y,-x)`

`rArrA(4,1)toA'(1,-4)" where A' is the image of A"`

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

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

`rArrulb-ulc=4ula'-4ulc`

`rArr3ulc=4ula'-ulb`

`color(white)(rArr3ulc)=4((1),(-4))-((5),(9))`

`color(white)(rArr3ulc)=((4),(-16))-((5),(9))=((-1),(-25))`

`rArrulc=1/3((-1),(-25))=((-1/3),(-25/3))`

`rArrC=(-1/3,-25/3)`