函数y=cosx+cos(x+π/3)

y=cosx+cos(x+π/3)
=cosx+cosxcos(π/3)-sinxsin(π/3)
=3cosx/2-√3sinx/2
=√3(sin(π/3)cosx-cos(π/3)sinx)
=√3sin(π/3-x)
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但其实可以不用化到最后,asinx+bcosx的形式最大值就是√(a^2+b^2)
因为asinx+bcosx=√(a^2+b^2)tg(x+β) 其中tgβ=b/a