已知cosx-cosy=1/3,求cosy-2(sinx)^2的最大值.
已知cosx-cosy=1/3,求cosy-2(sinx)^2的最大值.
数学人气:166 ℃时间:2020-02-04 10:19:39
优质解答
∵cosy=cosx-1/3∴原式=cosx-2*(1-cosx^2)-1/3= cosx-2+2cosx^2-1/3=2cosx^2+cosx-7/3设f(x)=2cosx^2+cosx-7/3f’(x)=-4cosxsinx-sinx=0sinx=0,x1=2kπ, x2=2kπ+π; -4cosx-1=0,cosx=-1/4,x3=2kπ-arcos(-1/4) ,x4=...
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