1. We are asked to solve the integral $$\int x \sin(x) \cos(x) \, dx$$.
2. Use the double-angle identity for sine: $$\sin(2x) = 2 \sin(x) \cos(x)$$, so $$\sin(x) \cos(x) = \frac{\sin(2x)}{2}$$.
3. Substitute into the integral:
$$\int x \sin(x) \cos(x) \, dx = \int x \frac{\sin(2x)}{2} \, dx = \frac{1}{2} \int x \sin(2x) \, dx$$.
4. Use integration by parts for $$\int x \sin(2x) \, dx$$:
Let $$u = x$$, so $$du = dx$$.
Let $$dv = \sin(2x) dx$$, so $$v = -\frac{\cos(2x)}{2}$$.
5. Apply integration by parts formula:
$$\int u \, dv = uv - \int v \, du$$
6. Calculate:
$$\int x \sin(2x) \, dx = -\frac{x \cos(2x)}{2} + \frac{1}{2} \int \cos(2x) \, dx$$
7. Integrate $$\int \cos(2x) \, dx$$:
$$\int \cos(2x) \, dx = \frac{\sin(2x)}{2} + C$$
8. Substitute back:
$$\int x \sin(2x) \, dx = -\frac{x \cos(2x)}{2} + \frac{1}{2} \cdot \frac{\sin(2x)}{2} + C = -\frac{x \cos(2x)}{2} + \frac{\sin(2x)}{4} + C$$
9. Recall the factor $$\frac{1}{2}$$ outside the integral:
$$\int x \sin(x) \cos(x) \, dx = \frac{1}{2} \left(-\frac{x \cos(2x)}{2} + \frac{\sin(2x)}{4}\right) + C = -\frac{x \cos(2x)}{4} + \frac{\sin(2x)}{8} + C$$
10. The answer matches option c): $$-\frac{x}{4} \cos(2x) + \frac{1}{8} \sin(2x) + C$$.
Integral X Sin Cos D2951E
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