Question

Points A and B are at `(5 ,9 )` and `(3 ,2 )`, respectively. Point A is rotated counterclockwise about the origin by `pi/2` and dilated about point C by a factor of `3`. If point A is now at point B, what are the coordinates of point C?

Answer 1

`C=(-15,13/2)`

Explanation:

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

`• " a point "(x,y)to(-y,x)`

`rArrA(5,9)toA'(-9,5)" where A' is the image of A"`

`rArrvec(CB)=color(red)(3)vec(CA')`

`rArrulb-ulc=3(ula'-ulc)`

`rArrulb-ulc=3ula'-3ulc`

`rArr2ulc=3ula'-ulb`

`color(white)(rArr2ulc)=3((-9),(5))-((3),(2))`

`color(white)(rArr2ulc)=((-27),(15))-((3),(2))=((-30),(13))`

`rArrulc=1/2((-30),(13))=((-15),(13/2))`

`rArrC=(-15,13/2)`