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

In any `Delta A B C` , prove that: `(cosA)/(bcosC+c cosB)+(cosB)/(c cosA+acosC)+(cosC)/(acosB+bcosA)=(a^2+b^2+c^2)/(2a b c)`

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From projection formula `a cosB + b cos A = C `
`a cosC+ c cos C = B`
`b cosC + c cos B = A`
Also by cosine law,
`cosA = (b^2 + c^2 - a^2)/(2bc)`
`cosB= (a^2 + c^2 - b^2)/(2ca)`
`cosC= (b^2 + a^2 - c^2)/(2ba)`
...
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