在△ABC中,若(sinB+sinC):(sinC+sinA):(sinA+sinB)=4:5:6,求其最大角的角度.
A.60° B.90° C.120° D.150°
人气:480 ℃ 时间:2020-04-12 08:47:06
解答
根据正弦定理得:
(b/2R+c/2R):(a/2R+c/2R):(a/2R+b/2R)=4:5:6
化简得:a:b:c=7:5:3,
最大角A,cosA=(5^2+3^2-7^2)/(2×5×3)=-1/2
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