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问题: 函数

Y=sin(x-3/π)+sinx取最大值X是?

解答:

解:y=sin(x-π/3)+sinx
=sinxcos(π/3)-cosxsin(π/3)+sinx
=(3/2)sinx-(√3/2)cosx
=√3[(√3/2)sinx-(1/2)cosx]
=√3[sinxcos(π/6)-cosxsin(π/6)]
=√3sin(x-π/6)≤√3
当且仅当sin(x-π/6)=1,即x=2kπ+2π/3时y取得最大值√3。