po是45度所以,P点的横纵坐标相等3cosa=4sina所以,cosa/sina = 4/3sina/cosa= 3/4典型的3,4,5直角三角形,自己画个图cosa= 4/5,sina= 3/5x= 3cosa = 3*（4/5）= 12/5y= 4sina = 4*(3/5)=12/5P(12/5,12/5)...