The Total solution for NCERT class 6-12
(1 + cot2 A)sin2 A = 1L.H.S. = (1 + cot2 A) (sin2 A)= cosec2 A sin2 A {1 + cot2 A =cosec2 A}= [cosec A sin A]2= (1)2= 1 = R.H.S. (∵sin A cosec A = 1