If x, y and z are proportional to the cosines of angles A, B and C of the triangle ABC respectively then prove that (y+z)tan((B-C)/2)cotA/2 + (z+x)tan((C-A)/2)cotB/2 + (x+y)tan((A-B)/2)cotC/2 = 0
If x, y and z are proportional to the cosines of angles A, B and C of the triangle ABC respectively then prove that
(y+z)tan((B-C)/2)cotA/2 + (z+x)tan((C-A)/2)cotB/2 + (x+y)tan((A-B)/2)cotC/2 = 0










