Question

Differentiate the function with respect to x:

cos (a cos x + b sin x), for some constant a and b.

Answer 1

Let, y = cos (a cos x + b sin x)

On differentiating with respect to x,

`dy/dx` = −sin (a cos x + b sin x) [a (−sin x) + b cos x]

= −sin (a cos x + b sin x) [−a sin x + b cos x]

= (a sin x − b cos x) sin (a cos x + b sin x)