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问题: 判断三角形

已知函数f(x) =(sinx-cosx)sinx,x属于实数,则f(x)最小正周期是?

解答:

已知函数f(x) =(sinx-cosx)sinx,x属于实数,则f(x)最小正周期是?
解:f(x) =(sinx-cosx)sinx
=sin²x-sinxcosx
=(1-cos2x)/2+1/2sin2x
=1/2sin2x-1/2cos2x+1/2
=√2/2sin(2x-π/4)+1/2
f(x)最小正周期是2π/2=π