已知cosx+siny=1/2,求siny-cosx平方的最值,要具体过程!在线等!

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cosx + siny = 1/2 (1)Taking derivative to the both side w.r.t x-sinx + cosy dy/dx =0dy/dx = sinx/cosyS = (siny - cosx)^2= (cosx + siny)^2 - 4sinycosx= 1/4 - 4sinycosxdS/dx = -4[ -siny sinx + cosx cos ...
======以下答案可供参考======
供参考答案1:
cosx+siny=1/2 平方得 (cosx+siny)^2=1/4 展开得 (cosx）^2 +(siny)^2+2cosxsiny=1/4
因为 (cosx）^2 +(siny)^2=1，所以2cosxsiny=-3/4
（siny-cosx）^2=(cosx）^2 +(siny)^2-2cosxsiny=1-(-3/4)=7/4