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In DeltaABC, Prove that: cosA+cosB+cos...

In `DeltaABC`, Prove that:
`cosA+cosB+cosC=1+4sinA/2sinB/2sinC/2`

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LHS. =cosA + cosB + cosC
`=2cos (A+B)/(2).cos(A-B)/(2) + cos C` (Apply C and D formula in first two terms)
`=2cos[(pi-C)/(2)]cos(A-B)/(2) +1-2sin^(2)C/2`
`=2sinC/2[cos(A-B)/(2)-sinC/2]+1`
`=1+2sinC/2[cos(A-B)/(2) -sin(180-A-B)/(2)]`
`=1+2sinC/2 xx sinA/2. sinB/2`
`=1+4 sinA/2. B/2. sinC/2`
=R.H.S.
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AAKASH INSTITUTE-TRIGNOMETRIC FUNCTIONS -Section - J (Akash Challengers Question)
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