10. Let f(x) = sin(2x + 1) and g(x) = x3 + 3 for all real x. Which of the following is equal to the derivative of the composite function f[g(x)]?

A. sin(2x3 + 7)

B. cos(2x3 + 7)

C. 6 sin(2x3 + 7)

D. 6 cos(2x3 + 7)

E. 6x2 cos(2x3 + 7)

 

Solution: The answer is E

 

First find the composite function f[g(x)] and then differentiate with respect to x.

The composite function f[g(x)] is defined as,

Use the Chain Rule to differentiate with respect to x as follows,