函數(shù)y=log(1/2)cos(3π/2-2x)的單調(diào)增區(qū)間是[-π/4+kπ,kπ)(k∈z),為什么?新年快樂(lè)哦!
函數(shù)y=log(1/2)cos(3π/2-2x)的單調(diào)增區(qū)間是[-π/4+kπ,kπ)(k∈z),為什么?新年快樂(lè)哦!
優(yōu)質(zhì)解答
cos(3π/2-2x)=-sin2x
log1/2x遞減
所以y遞增則真數(shù)-sin2x遞減
即sin2x遞增
且真數(shù)大于0
所以sin2x<0
sin遞增且小于0
2kπ-π/2<2x<2kπ
kπ-π/4