sec4x-tan4x=1+ 2tan2x
sec4x-tan4x
(1 + tan^2 x) ^2 -tan4x (because 1+ tan ^2 x= sec^2x )
1+tan4x + 2tan^2 x -tan4x =1+ 2tan2x
sec4x-tan4x=1+ 2tan2x
sec4x-tan4x
(1 + tan^2 x) ^2 -tan4x (because 1+ tan ^2 x= sec^2x )
1+tan4x + 2tan^2 x -tan4x =1+ 2tan2x