N
nhokdangyeu01


1
$cos2x + 2cosx + sinx = cosx . ( cos2x - sin2x )$
2
$tan^4x + 1 = \dfrac{( 2 - sin^22x) . sin3x}{cos^4x}$
$cos2x + 2cosx + sinx = cosx . ( cos2x - sin2x )$
2
$tan^4x + 1 = \dfrac{( 2 - sin^22x) . sin3x}{cos^4x}$