Composite Derivatives
1. **Problem 1: Find the derivative of** $y=\cos(\sin(x))$.
2. Let $f(u)=\cos(u)$ and $g(x)=\sin(x)$ so that $y=f(g(x))$.
3. Using the chain rule: $$\frac{dy}{dx} = f'(g(x)) \cdot g'(x)$$
4. Calculate derivatives:
- $f'(u) = -\sin(u)$
- $g'(x) = \cos(x)$
5. Substitute back:
$$\frac{dy}{dx} = -\sin(\sin(x)) \cdot \cos(x)$$
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6. **Problem 2: Find the derivative of** $y = e^{9\sqrt{x}}$.
7. Let $f(u) = e^{u}$ and $g(x) = 9\sqrt{x} = 9x^{1/2}$ so that $y = f(g(x))$.
8. Using the chain rule:
$$\frac{dy}{dx} = f'(g(x)) \cdot g'(x)$$
9. Calculate derivatives:
- $f'(u) = e^{u}$
- $g'(x) = 9 \cdot \frac{1}{2} x^{-1/2} = \frac{9}{2\sqrt{x}}$
10. Substitute back:
$$\frac{dy}{dx} = e^{9\sqrt{x}} \cdot \frac{9}{2\sqrt{x}} = \frac{9}{2\sqrt{x}} e^{9\sqrt{x}}$$