cos(a-b=-1/3)(化简)已知cos(a-b)=-1/3 化简(sina+sinb)的平方+(cosa+cosb)的平方
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![cos(a-b=-1/3)(化简)已知cos(a-b)=-1/3 化简(sina+sinb)的平方+(cosa+cosb)的平方](/uploads/image/z/2469906-18-6.jpg?t=cos%28a-b%3D-1%2F3%29%28%E5%8C%96%E7%AE%80%29%E5%B7%B2%E7%9F%A5cos%28a-b%29%3D-1%2F3+%E5%8C%96%E7%AE%80%EF%BC%88sina%2Bsinb%EF%BC%89%E7%9A%84%E5%B9%B3%E6%96%B9%2B%EF%BC%88cosa%2Bcosb%EF%BC%89%E7%9A%84%E5%B9%B3%E6%96%B9)
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cos(a-b=-1/3)(化简)已知cos(a-b)=-1/3 化简(sina+sinb)的平方+(cosa+cosb)的平方
cos(a-b=-1/3)(化简)
已知cos(a-b)=-1/3 化简(sina+sinb)的平方+(cosa+cosb)的平方
cos(a-b=-1/3)(化简)已知cos(a-b)=-1/3 化简(sina+sinb)的平方+(cosa+cosb)的平方
cos(a-b)=-1/3
cosacosb+sinasinb=-1/3
(sina+sinb)^2+(cosa+cosb)^2
=(sina)^2+(sinb)^2+2sinasinb+(cosa)^2+(cosb)^2+2cosacosb
=(sina)^2+(cosa)^2+(sinb)^2+(cosb)^2+2(cosacosb+sinasinb)
=1+1-2/3
=4/3