已知sinx siny=1/3,求u=sinx-cosy的平方的最大值与最小值
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sinx +siny=1/3,==-2/3≤siny≤1,u=sinx-cosy^2=1/3-siny-1+siny^2=(siny-1/2)^2-11/12,最大值=(-2/3-1/2)^2-11/12=4/9,最小值=-11/12.
已知sinx siny=1/3,求u=sinx-cosy的平方的最大值与最小值
sinx +siny=1/3,==-2/3≤siny≤1,u=sinx-cosy^2=1/3-siny-1+siny^2=(siny-1/2)^2-11/12,最大值=(-2/3-1/2)^2-11/12=4/9,最小值=-11/12.