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[函数] 一眼看尽A角

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isee Posted 2021-8-4 22:59 |Read mode

若在三角形`ABC`中若`2a\cos A+c\cos B+b\cos C=0`，则角`A=`______.

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色k Posted 2021-8-4 23:36

？这不是直接射影定理吗？

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Author| isee Posted 2021-8-4 23:41

回复 2# 色k

嗯，也是第一余弦定理，看尽了，达到目的的

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