1- sin(2π/3 - a)/sina

题目

1- sin(2π/3 - a)/sina

答案

因为2π/3 在Y轴负半轴上,
则2π/3-a在第3象限上
则sin(2π/3-a)=-cosa
1- sin(2π/3 - a)/sina
=1+cosa/sina
=1+cota