Question

If f(x) = 7x^6cos^-1x, find f '(x).

Answer 1

y = 7 x^6 cos^-1 x

f' = 7[ x^6 (1/(1-x^2)) + 6x^5 cos^-1 x ]

= 7 x^6/(1-x^2) + 42x^5 cos^-1 x

Answer 2

d/dx cos^-1(x) = -1/√(1-x^2)