2tan(派/4-X)SIN^2(派/4+X)化简

题目

2tan(派/4-X)SIN^2(派/4+X)化简

答案

原式=2cot[派/2-(派/4-X)]sin^2(派/4+X)=2cot(派/4+X)sin^2(派/4+X)
=2[cos(派/4+X)/sin(派/4+X)]sin^2(派/4+X)=2sin(派/4+X)cos(派/4+X)
=sin2(派/4+X)]=sin(派/2+2X)]=cos2X