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**Homework Statement**

Differentiate sin x - 1/3 sin^3 (x) + 7

**The attempt at a solution**

sin x becomes cos x, and 7 becomes 0.

Using the product rule on (1/3) sin^3 (x) + 7 I get:

(0) sin^3 x + (1/3) [derivative of sin^3 (x)]

Getting the derivative of sin^3(x) is the tricky part I'm struggling with.

I would have thought it would be 3 sin^2 (x) times cos^3(x); but I know this is wrong.