Question

differentiate

y = (cos x)/ (x^9)

Answer 1

y = (x^-9)cos x

dy/dx = (x^-9)(-sin x ) - 9 cos x (x^-10)
= - x^-10 (x sin x) - 9 x^-10 (cos x)
= -(x sin x + 9 cos x)/x^10