已知▲ABC中,角A.B.C所对的边分别是a.b.c,(a+b+c)*(a+b-c)=3ab ,求若c=2 △abc的最大面积值?
2011-05-07
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(a+b+c)拿誉*(a+b-c)=3ab ,
(a+b)^2 - c^2 = 3ab
(a+b)^2 = 4+ 3ab >= 4ab
ab <= 4
cos C = (a^2+b^2-c^2) /肢凯 (2ab) = 1/2
sin C = 根号3/2
△abc的面积为 1/2 ab*sinC = 根号3/4 * ab <= 根号消饥段3
(a+b)^2 - c^2 = 3ab
(a+b)^2 = 4+ 3ab >= 4ab
ab <= 4
cos C = (a^2+b^2-c^2) /肢凯 (2ab) = 1/2
sin C = 根号3/2
△abc的面积为 1/2 ab*sinC = 根号3/4 * ab <= 根号消饥段3
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