证明cos(x)/sin(x)+sin(x)/cos(x)=2/sin(2x)同上

问题描述:

证明cos(x)/sin(x)+sin(x)/cos(x)=2/sin(2x)
同上

通分即可

通分
左边=(cos²x+sin²x)/sinxcosx
=1/sinxcosx
=2/2sinxcosx
=2/sin2x
=右边
命题得证