设向量a=(cosx,sinx)b=(cosy,siny),其中0
人气:244 ℃ 时间:2020-04-08 22:16:57
解答
|2a+b|=|a-2b|两边同时平方 得4a^2+4ab+b^2=a^2-4ab+4b^2 (*)又 a=(cosx,sinx) b=(cosy,siny)所以|a|=1 |b|=1 所以(*)式化简得8ab=0 即cosx*cosy+sinx*siny=cos(x-y)=0
又0
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