(cos3x−sin3x+sin4x)\ (1-2 ( cosx.cos5pi/2 -sinx.sin5pi/2)^2) = 2sin2x-1
x+sin4x(cos3x−sin3x+sin4x)\ ( 1-2sin ^2 x ) = 2 sin2x -1
(cos3x−sin3x+sin4x)\ ( cos 2x ) = 2 sin 2x -1
cos3x−sin3x+sin4x=sin4x -cos 2x
cos3x−sin3x + cox ^2 x - sin ^2 x =0
( cos x -sin x) ( 1 + sinx. cosx + sinx+ cosx)=0