化简(sina+cosa-1)(sina-cosa+1)/sin2a

问题描述:

化简(sina+cosa-1)(sina-cosa+1)/sin2a
如题.

(sina+cosa-1)(sina-cosa+1)/sin2a
=(2sina/2cosa/2-2sin^2 a/2)(2sina/2cosa/2+2sin^2a/2)/4sina/2cosa/2cosa
=sina/2*(cosa/2-sina/2)(cosa/2+sina/2)/cosa/2cosa
=sina/2*(cos^2a/2-sin^2a/2) / cosa/2cosa
=sina/2cosa / cosa/2cosa
=tana/2