化简函数f(x)=cos2x/sin(45'-x)
问题描述：
化简函数f(x)=cos2x/sin(45'-x)
答
f(x)=cos2x/sin(45°-x)
= (cos^2x-sin^2x)/(sin45°cosx-cos45°sinx)
= (cosx+sinx)(cosx-sinx) / [√2/2(cosx-sinx)]
= √2(cosx+sinx)
= 2(sinxcos45°+cosxsin45°)
= 2sin(x+45°)