`Delta ABC` में सिद्ध कीजिए कि -
` a (cos^(2) . C/2 - cos^2. B/2) = (b-c) * cos^(2) . A/2 `

Explanation

` L.H.S = a( cos^(2).C/2 - cos^(2).B/2)`
` = a [ (s(s-c))/(ab)- (s(s-b))/(ac) ] `
` = a* s/a [ (s-c)/b - (s-b)/c]`
` = s [ (cs-c^(2)-bs+b^(2))/(bc)]`
` = s/(bc) [ (b^(2)-c^(2))-bs+cs]`
` s/(bc) [ (b-c)(b+c)-(b-c)*s]`
` = s/ (ab) * ( b-c) (b+c-s)`
` = (b-c) (s(2s-a-s))/(bc)`
` = ( b-c) (s(s-a))/(bc)`
` = ( b-c) * cos^(2) . A/2 = R.H.S`