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In any Delta A B C , prove that: (cos A...

In any ` Delta A B C ,` prove that: `(cos A)/a+(cos B)/b+(cos C)/c=(a^2+b^2+c^2)/(2a b c)`

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`LHS`
`=(b^{2}+c^{2}-a^{2}) / (2 a b c)+(c^{2}+a^{2}-b^{2}) / (2 a b c)+(a^{2}+b^{2}-c^{2}) / (2 a b c) `
`=(a^{2}+b^{2}+c^{2}) / (2 a b c )`
`= RHS `
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