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If A+B+ C =pi, then prove that cos ^(2) ...

If `A+B+ C =pi`, then prove that `cos ^(2) (A/2)+ cos ^(2) (B/2) +cos ^(2) (C/2)=2(1+sin . (A)/(2) sin. (B)/(2) sin. (C)/(2))`

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The correct Answer is:
`=(1+ sin. (A)/(2) sin. (B)/(2)sin. (C)/(2))=R.H.S`
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