Question

If A,B and C are the interior angles of a triangle,then prove that cosec 2 (B+C /2) - tan 2 A/2 = 1.

Answer 1

cosec 2(B+C/2) = sec 2  A/2    as  A+B+C/2  =  90
sin  90 --A/2 = cos  A/2    SO
sec 2  A/2 -- tan 2  A/2 = 1