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数学
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已知三角形的内角ABC的对边abc满足b的平方加c 的平方减a的平方等于bc,求角A
救命
人气:320 ℃ 时间:2019-08-18 14:45:39
解答
由三角形余弦原理知:
cosA=(b^2+c^2-a^2)/(2bc)
b^2+c^2-a^2=2bccosA
因为b^2+c^2-a^2=bc
所以2bccosA=bc
cosA=1/2
A=60
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