3/(sin20^2)-1/(cos20^2)+64sin20^2的值是?cos20cos40cos80的值是?已知a,b均为锐角,且满足3sina^2+2sinb^2=1,3sin2a-2sin2b=0,求证a+2b=90度
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![3/(sin20^2)-1/(cos20^2)+64sin20^2的值是?cos20cos40cos80的值是?已知a,b均为锐角,且满足3sina^2+2sinb^2=1,3sin2a-2sin2b=0,求证a+2b=90度](/uploads/image/z/4343799-39-9.jpg?t=3%2F%28sin20%5E2%29-1%2F%28cos20%5E2%29%2B64sin20%5E2%E7%9A%84%E5%80%BC%E6%98%AF%3Fcos20cos40cos80%E7%9A%84%E5%80%BC%E6%98%AF%3F%E5%B7%B2%E7%9F%A5a%2Cb%E5%9D%87%E4%B8%BA%E9%94%90%E8%A7%92%2C%E4%B8%94%E6%BB%A1%E8%B6%B33sina%5E2%2B2sinb%5E2%3D1%2C3sin2a-2sin2b%3D0%2C%E6%B1%82%E8%AF%81a%2B2b%3D90%E5%BA%A6)
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