求证:1+cos2a+2sin^2a=2

问题描述:

求证:1+cos2a+2sin^2a=2

可乐快乐呵呵呵,
证明:
cos2a=cos^2a-sin^2a
所以1+cos2a+2sin^2a
=1+cos^2a-sin^2a+2sin^2a
=1+cos^2a+sin^2a
=1+1
=2