2cos^2a-2sin^2a=1,求a

问题描述:

2cos^2a-2sin^2a=1,求a

2cos^2a-2sin^2a=1
2cos2a=1
cos2a=1/2
2a=2kπ±π/3
a=kπ±π/6a属于(0,90),求a的值?a=π/6