Integration Problems Aa0E26
1. **Problem (a):** Determine $\int (1 - t)^2 \, dt$.
2. **Formula and rules:** Use the power rule for integration: $\int x^n \, dx = \frac{x^{n+1}}{n+1} + C$ for $n \neq -1$.
3. **Step-by-step solution (a):**
- Expand the integrand: $(1 - t)^2 = 1 - 2t + t^2$.
- Integrate term-by-term:
$$\int (1 - 2t + t^2) \, dt = \int 1 \, dt - 2 \int t \, dt + \int t^2 \, dt$$
- Calculate each integral:
$$= t - 2 \cdot \frac{t^2}{2} + \frac{t^3}{3} + C = t - t^2 + \frac{t^3}{3} + C$$
4. **Answer (a):**
$$\int (1 - t)^2 \, dt = t - t^2 + \frac{t^3}{3} + C$$
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5. **Problem (b)(i):** Evaluate $\int_1^3 (x^2 - 4x + 3) \, dx$.
6. **Step-by-step solution (b)(i):**
- Integrate the function:
$$\int (x^2 - 4x + 3) \, dx = \frac{x^3}{3} - 2x^2 + 3x + C$$
- Evaluate definite integral from 1 to 3:
$$\left[ \frac{x^3}{3} - 2x^2 + 3x \right]_1^3 = \left( \frac{27}{3} - 2 \cdot 9 + 9 \right) - \left( \frac{1}{3} - 2 + 3 \right)$$
$$= (9 - 18 + 9) - \left( \frac{1}{3} + 1 \right) = 0 - \frac{4}{3} = -\frac{4}{3}$$
7. **Answer (b)(i):**
$$\int_1^3 (x^2 - 4x + 3) \, dx = -\frac{4}{3}$$
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8. **Problem (b)(ii):** Evaluate $\int_0^2 3 \sin t \, dt$.
9. **Step-by-step solution (b)(ii):**
- Integrate:
$$\int 3 \sin t \, dt = -3 \cos t + C$$
- Evaluate definite integral from 0 to 2:
$$\left[-3 \cos t \right]_0^2 = -3 \cos 2 + 3 \cos 0 = -3 \cos 2 + 3$$
10. **Answer (b)(ii):**
$$\int_0^2 3 \sin t \, dt = 3 - 3 \cos 2$$
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11. **Problem (c):** Sketch curves $y = x^2 + 3$ and $y = 7 - 3x$ and find the area enclosed by integration.
12. **Step 1: Find intersection points by solving:**
$$x^2 + 3 = 7 - 3x$$
$$x^2 + 3x - 4 = 0$$
Factor:
$$(x + 4)(x - 1) = 0$$
So, $x = -4$ or $x = 1$.
13. **Step 2: Set up the integral for the area between curves:**
The line is above the parabola between $x = -4$ and $x = 1$, so area:
$$A = \int_{-4}^1 \left[(7 - 3x) - (x^2 + 3)\right] \, dx = \int_{-4}^1 (4 - 3x - x^2) \, dx$$
14. **Step 3: Integrate:**
$$\int (4 - 3x - x^2) \, dx = 4x - \frac{3x^2}{2} - \frac{x^3}{3} + C$$
15. **Step 4: Evaluate definite integral:**
$$\left[4x - \frac{3x^2}{2} - \frac{x^3}{3}\right]_{-4}^1 = \left(4(1) - \frac{3(1)^2}{2} - \frac{1^3}{3}\right) - \left(4(-4) - \frac{3(-4)^2}{2} - \frac{(-4)^3}{3}\right)$$
$$= \left(4 - \frac{3}{2} - \frac{1}{3}\right) - \left(-16 - \frac{3 \cdot 16}{2} + \frac{64}{3}\right)$$
$$= \left(4 - 1.5 - 0.3333\right) - \left(-16 - 24 + 21.3333\right)$$
$$= 2.1667 - (-18.6667) = 2.1667 + 18.6667 = 20.8334$$
16. **Answer (c):**
The area enclosed by the curves is approximately $20.833$ square units.
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**Summary:**
- (a) $\int (1 - t)^2 dt = t - t^2 + \frac{t^3}{3} + C$
- (b)(i) $\int_1^3 (x^2 - 4x + 3) dx = -\frac{4}{3}$
- (b)(ii) $\int_0^2 3 \sin t dt = 3 - 3 \cos 2$
- (c) Area enclosed by $y = x^2 + 3$ and $y = 7 - 3x$ is approximately $20.833$.