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In any triangle A B C , prove that follo...

In any triangle `A B C` , prove that following: `\ \ bcosB+c\ cos\ C=a cos(B-C)`

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By using sine rule `a/sinA=b/sinB=c/sinC=k`...........(1)
`:.`R.H.S.=`acos(B-C)=ksinAcos(B-C)`.......by using (1)
`=ksin(B+C)cos(B-C)`
`k/2sin(B+C)cos(B-C)=k/2[sin2B+sin2C]`
...
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