Sinceyou are findingthe rotationof the image counterclockwiseaboutthe origin,you will find the op-positeof the -coordinatesand then reversethe order. So, the coordinatechangecan be expressedas
follows.
Carefullyadjusteachcoordinateusingthe formulaabove.This givesnew coordinates , , and.Finally, we drawthe rotatedtriangleto verifythat your answeris correct.