求证：sina(1+cos2a)=sin2a*cosa.

分类: 作业答案 • 2021-12-18 22:37:58

问题描述：

答

sina(1+cos2a)=sina*2*(cosa)^2.
=sin2a*cosa

答

sina(1+cos2a)
=sina(1+2cos^2 a - 1)
=sina×2cos^2a
=2sinacosa × cosa
=sin2a ×cosa

答

sina(1+cos2a)
=sina(1+2cos^2a-1)
=(2sina*cosa)*cosa
=sin2a*cosa