1. **State the problem:** Find the first derivative $f'(x)$ and the second derivative $f''(x)$ of the function $$f(x) = -2 \sin\left(\frac{1}{2}x - 1\right).$$
2. **Recall the derivative rules:**
- The derivative of $\sin(u)$ with respect to $x$ is $\cos(u) \cdot u'$, where $u$ is a function of $x$.
- The derivative of a constant times a function is the constant times the derivative of the function.
3. **Find the first derivative $f'(x)$:**
$$f'(x) = -2 \cdot \frac{d}{dx} \sin\left(\frac{1}{2}x - 1\right) = -2 \cdot \cos\left(\frac{1}{2}x - 1\right) \cdot \frac{d}{dx} \left(\frac{1}{2}x - 1\right).$$
4. **Calculate the inner derivative:**
$$\frac{d}{dx} \left(\frac{1}{2}x - 1\right) = \frac{1}{2}.$$
5. **Substitute back:**
$$f'(x) = -2 \cdot \cos\left(\frac{1}{2}x - 1\right) \cdot \frac{1}{2} = \cancel{-2 \cdot \frac{1}{2}} \cdot \cos\left(\frac{1}{2}x - 1\right) = -1 \cdot \cos\left(\frac{1}{2}x - 1\right) = -\cos\left(\frac{1}{2}x - 1\right).$$
6. **Find the second derivative $f''(x)$:**
$$f''(x) = \frac{d}{dx} \left(-\cos\left(\frac{1}{2}x - 1\right)\right) = - \cdot \frac{d}{dx} \cos\left(\frac{1}{2}x - 1\right) = - \left(-\sin\left(\frac{1}{2}x - 1\right) \cdot \frac{1}{2}\right).$$
7. **Simplify:**
$$f''(x) = - \left(-\sin\left(\frac{1}{2}x - 1\right) \cdot \frac{1}{2}\right) = \cancel{-1 \cdot -\frac{1}{2}} \sin\left(\frac{1}{2}x - 1\right) = \frac{1}{2} \sin\left(\frac{1}{2}x - 1\right).$$
**Final answers:**
$$f'(x) = -\cos\left(\frac{1}{2}x - 1\right), \quad f''(x) = \frac{1}{2} \sin\left(\frac{1}{2}x - 1\right).$$
Derivatives Sine 03C11E
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