chain rule

Let y be a function of x.

Chain rule,

dy/dx = (dy/du)(du/dx)               .... multiply and divide by du

y = sinⁿx  = uⁿ  ........... where u = sin x

then dy/du = nu^n-1

du/dx = cos x

and

dy/dx = (dy/du)(du/dx) = nu^n-1cos x = nsin^n-1x cos x 

Regards,

Team,

TopperLearning.