sina乘以sina=sin(30+b)sin(30-b)+sinb乘以sinb 求a的大小向量AB乘以向量AC=12且a=2倍根号下7 求c、b(b小于c)
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sina乘以sina=sin(30+b)sin(30-b)+sinb乘以sinb 求a的大小向量AB乘以向量AC=12且a=2倍根号下7 求c、b(b小于c)
sina乘以sina=sin(30+b)sin(30-b)+sinb乘以sinb 求a的大小
向量AB乘以向量AC=12且a=2倍根号下7 求c、b(b小于c)
sina乘以sina=sin(30+b)sin(30-b)+sinb乘以sinb 求a的大小向量AB乘以向量AC=12且a=2倍根号下7 求c、b(b小于c)
设cosA =b/c,sinB=b/c,cosB=a/c,sinA=a/c(c为斜边)
根据题意知此三角形为等腰直角三角形
即a=b,则cosA=cosB
等式两边可约去cosA和cosB
则有sinB=sinA
整理得:sinA-sinB=0,即·sin(A-B)=0