sina+cosa=0.2所以cosa=0.2-sina由sina^2+cosa^2=1所以：sina^2+(0.2-sina)^2=1 sina=o.8或者-0.6斜率=taga=sina/cosa=0.8/(0.2-0.8)=-1.33或者=taga=sina/cosa=-0.6/(0.2-(-0.6))=-1.5