1.y=(sina-4cosa)/(5sina+2cosa)=（tana-4）/（5tana+2）=-1/62.原式=4sinacosa+sina^2+cosa^2=(4sinacosa+sina^2+cosa^2)/(sina^2+cosa^2)=(4tana+tana^2+1)/(tana^2+1)=13/5
