sin(α-4分之π)分之cos2α=—2分之根号2 求cosα+sinα

问题描述:

sin(α-4分之π)分之cos2α=—2分之根号2 求cosα+sinα

化简后得(cosa)²-(sina)²/sinacosπ/4-cosasinπ/4 =-√2/2
(cosa+sina)(cosa-sina)/√2/2(sina-cosa)=-√2/2
cosa+sina=1/2