If A + B + C = `180^(@)` then P.T.
`"cos "(A)/(2) + sin ((B - C)/(2)) = 2 "sin" (B)/(2) "cos" (C )/(2)`

If A + B + C = 180^(@) then P.T. cos A + cos (B - C) = 2 sin B sin C

If A + B + C = 180^(@) then P.T. sum tan ""(A)/(2) tan ""(B)/(2) = 1 . If A, B, C are + ve

If A, B , C are angles of a triangle, then P. T sin ^(2) . (A)/(2)+ sin^(2). (B)/(2) - sin ^(2). (C)/(2) =1-2 cos. (A)/(2) cos. (B)/(2) sin .(C)/(2)

If A+B+C=90^(@) then (cos 2A+cos 2B+cos 2C-1)/(sin A sin B sin C)=

If A+B+C= 180^(@) , " then " ( sin 2A- sin 2B- sin 2C)/(sin 2B- sin 2A - sin 2C)=

If A+ B+C= 180^(@) " then " cos 2A+ cos 2B + cos 2C+ 1=

( a- b) ^(2) cos ^(2) ""(C ) /(2) + ( a+b) ^(2) sin ^(2) "" ( C )/(2) =

If A+B+C=180^(@) " then " sin^(2)""(A)/(2)+sin^(2)""(B)/2+sin^(2)""(C)/(2)=

If A+B+C=180^@ " then " sin^(2)""(A)/(2)-sin^(2)""(B)/(2)+sin^(2)""(C)/(2)=