90 degree angle rotation counterclockwise geometry

Question

how can i get coordinates from -y,x if i rotate it 90 degrees clockwise

Answer 1

90 degree clockwise rotation transforms (x,y) into (y,-x)

(1,2) becomes) (2,-1)

whatever you start with, switch x with y and change the sign of the new y

(-45,9) becomes (9,45)