Integral Evaluation Ba8E52
1. **Problem 1a:** Evaluate the integral $$\int \sqrt[3]{1 - x^2} \, dx$$
- This is an integral involving a cube root of a quadratic expression.
- We can rewrite the integrand as $$(1 - x^2)^{\frac{1}{3}}$$.
- This integral does not have a simple elementary antiderivative, so it typically requires substitution or special functions.
2. **Problem 1b:** Evaluate the integral $$\int 3x^2 (x^3 + 5)^7 \, dx$$
- Use substitution: let $$u = x^3 + 5$$.
- Then, $$\frac{du}{dx} = 3x^2$$, so $$du = 3x^2 dx$$.
- The integral becomes $$\int u^7 \, du$$.
- Integrate: $$\int u^7 \, du = \frac{u^8}{8} + C$$.
- Substitute back: $$\frac{(x^3 + 5)^8}{8} + C$$.
3. **Problem 2a:** Evaluate the integral $$\int e^x \sin x \, dx$$
- Use integration by parts or recognize it as a standard integral.
- Let $$I = \int e^x \sin x \, dx$$.
- Integrate by parts twice or use the formula:
$$I = \frac{e^x}{2} (\sin x - \cos x) + C$$.
4. **Problem 2b:** Evaluate the integral $$\int x^2 e^{3x} \, dx$$
- Use integration by parts repeatedly.
- Let $$u = x^2$$, $$dv = e^{3x} dx$$.
- Then $$du = 2x dx$$, $$v = \frac{e^{3x}}{3}$$.
- First integration by parts:
$$\int x^2 e^{3x} dx = \frac{x^2 e^{3x}}{3} - \int \frac{2x e^{3x}}{3} dx$$.
- Second integration by parts on $$\int x e^{3x} dx$$:
Let $$u = x$$, $$dv = e^{3x} dx$$, so $$du = dx$$, $$v = \frac{e^{3x}}{3}$$.
- Then:
$$\int x e^{3x} dx = \frac{x e^{3x}}{3} - \int \frac{e^{3x}}{3} dx = \frac{x e^{3x}}{3} - \frac{e^{3x}}{9} + C$$.
- Substitute back:
$$\int x^2 e^{3x} dx = \frac{x^2 e^{3x}}{3} - \frac{2}{3} \left( \frac{x e^{3x}}{3} - \frac{e^{3x}}{9} \right) + C$$.
- Simplify:
$$= \frac{x^2 e^{3x}}{3} - \frac{2x e^{3x}}{9} + \frac{2 e^{3x}}{27} + C$$.
**Final answers:**
1a) $$\int (1 - x^2)^{1/3} dx$$ cannot be expressed in elementary functions simply.
1b) $$\frac{(x^3 + 5)^8}{8} + C$$
2a) $$\frac{e^x}{2} (\sin x - \cos x) + C$$
2b) $$\frac{x^2 e^{3x}}{3} - \frac{2x e^{3x}}{9} + \frac{2 e^{3x}}{27} + C$$