cos^2(派/8)-sin^2(5派/12)得多少?
问题描述:
cos^2(派/8)-sin^2(5派/12)得多少?
答
cos^2(派/8)-sin^2(5派/12)
=[1+cos(派/4)]/2-[1-cos(5派/6)]/2
=根号2/4-根号3/4