I. The derivative $$\frac{d}{dx} (x^2 * \sin(x))$$ is $$2*x*\sin(x) + x^2*\cos(x)$$.

II. Using the chain rule, $$\frac{d}{dx} \cos(3*x^2)$$ is $$-\sin(3*x^2) * 3$$.

III. The derivative of $$\tan(x)$$ is $$\sec^2(x)$$.

Which of these statements are true regarding differentiation techniques?