Question

y = cos 3x sin 4x find second derivative

Answer 1

First derivative = cos (3x) [4 cos 4x] + sin (4x) [-3sin 3x]
= 4 cos 4x cos 3x - 3 sin 4x sin 3x

Second derivative
= 4 [ cos4x(-3 sin 3x)+ cos3x(-4sin4x] -3[ sin4x(3cos3x) + sin3x(4cos4x)]
= -24 sin3x cos4x - 25 sin 4x cos 3x

Answer 2

Sin4xcosx

1/2 × 2sin4xcosx

1/2 × sin(4x+x) + cos(4x-x)

1/2 × sin5x+cos3x

Dy/d = 1/2 (5sin5x+3cos3x)

Simple:")