sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)=?

分类: 作业答案 • 2021-12-28 10:43:02

问题描述：

sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)=?
请问有何简便解法?

答

sin(x-20°)+cos(x+70°)+sin(x+20°)sec(70-x)
=sin(x-20°)+sin(20°-x)+sin(x-20°)/cos(70°-x)
=sin(x-20°)-sin(x-20°)+sin(x-20°)/sin(x-20°)
=0+1
=1