tribeking22
(tan^2 x - sin^2 x).cot^4 x = (sin^2 x/cos^2 x - sin^2 x).cos^4 x/sin^4 x = ((sin^2 x - sin^2 x cos^2 x)/cos^2 x) . cos^4 x/sin^4 x = (sin^2 x - sin^2 x cos^2 x) . cos^2 x/sin^4 x = sin^2 x . (1 - cos^2 x) . cos^2 x/sin^4 x = (1 - cos^2 x) . cos^2 x/sin^2 x = sin^2 x . cos^2 x/sin^2 x = cos^2 x
= (sin^2 x/cos^2 x - sin^2 x).cos^4 x/sin^4 x
= ((sin^2 x - sin^2 x cos^2 x)/cos^2 x) . cos^4 x/sin^4 x
= (sin^2 x - sin^2 x cos^2 x) . cos^2 x/sin^4 x
= sin^2 x . (1 - cos^2 x) . cos^2 x/sin^4 x
= (1 - cos^2 x) . cos^2 x/sin^2 x
= sin^2 x . cos^2 x/sin^2 x
= cos^2 x