已知三角形ABC 的外接圆半径是R 且2R(sinA方-sinC方)=(根号a-b)sinB,求角C
人气:216 ℃ 时间:2020-04-06 08:09:53
解答
2R((a/2R)^2-(c/2R)^2)=(a-b)b/2R
(a^2-c^2)/2R=(ab-b^2)/2R
a^2-c^2=ab-b^2
a^2+b^2-c^2=ab
a^2+b^2-c^2/2ab=1/2
cosC=1/2
C=60
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