◆◆◆求证sin^2a+sin^2β-sin^a*sin^2β+cos^2a*cos^2β=1

问题描述:

◆◆◆求证sin^2a+sin^2β-sin^a*sin^2β+cos^2a*cos^2β=1
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应是sin^2a+sin^2β-sin^2a*sin^2β+cos^2a*cos^2β=1

出错了吧?中间漏了个2?sin^2a+sin^2β-sin^2a*sin^2β+cos^2a*cos^2β=sin^2a-sin^2a*sin^2β+cos^2a*cos^2β+sin^2β=sin^2a*cos^2β+cos^2a*cos^2β+sin^2β=cos^2β*(sin^2a+cos^2a)+sin^2β=cos^2β+sin^2β=1...