11) Define A(k) = x dx Using area, create a nice formula for A(k). Explain your area reasoning. Using area, explain why f" sin(0) de = 0 Using area, explain why cos(0) de = 0

Calculus: Early Transcendentals
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ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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### Transcription and Explanation

#### Problem 11

**Define** 
\[ A(k) = \int_{0}^{k} x \, dx \]

Using area, create a nice formula for \( A(k) \). Explain your area reasoning.

**Explanation:**

To find the area under the curve \( y = x \) from \( x = 0 \) to \( x = k \), we recognize this as the area of a right triangle with a base of \( k \) and a height of \( k \). 

The area \( A \) of a triangle is given by:

\[ A = \frac{1}{2} \times \text{base} \times \text{height} \]

Substituting the values, we get:

\[ A(k) = \frac{1}{2} \times k \times k = \frac{k^2}{2} \]

Thus, \( A(k) = \frac{k^2}{2} \).

---

**Using area, explain why** 
\[ \int_{-\pi}^{\pi} \sin(\theta) \, d\theta = 0 \]

**Explanation:**

The function \( \sin(\theta) \) is symmetric about the origin, having the same area above the x-axis as it does below within the interval \([-π, π]\). The positive area from \([-π, 0]\) cancels out with the negative area from \([0, π]\). Therefore, the total area is zero.

---

**Using area, explain why** 
\[ \int_{0}^{\pi} \cos(\theta) \, d\theta = 0 \]

**Explanation:**

The function \( \cos(\theta) \) from \( 0 \) to \( \pi \) has equal positive and negative areas. \( \cos(\theta) \) is positive over \([0, \frac{\pi}{2}]\) and negative over \([\frac{\pi}{2}, \pi]\). These areas are equal in magnitude, thus cancel out, making the integral zero.

---

**Using area, explain why** 
\[ \int_{0}^{2} (t+5)(t-3) \, dt < 0 \]

**Explanation:**

First, expand the expression: 

\[ (t+5)(t-3) = t^2 - 3t
Transcribed Image Text:### Transcription and Explanation #### Problem 11 **Define** \[ A(k) = \int_{0}^{k} x \, dx \] Using area, create a nice formula for \( A(k) \). Explain your area reasoning. **Explanation:** To find the area under the curve \( y = x \) from \( x = 0 \) to \( x = k \), we recognize this as the area of a right triangle with a base of \( k \) and a height of \( k \). The area \( A \) of a triangle is given by: \[ A = \frac{1}{2} \times \text{base} \times \text{height} \] Substituting the values, we get: \[ A(k) = \frac{1}{2} \times k \times k = \frac{k^2}{2} \] Thus, \( A(k) = \frac{k^2}{2} \). --- **Using area, explain why** \[ \int_{-\pi}^{\pi} \sin(\theta) \, d\theta = 0 \] **Explanation:** The function \( \sin(\theta) \) is symmetric about the origin, having the same area above the x-axis as it does below within the interval \([-π, π]\). The positive area from \([-π, 0]\) cancels out with the negative area from \([0, π]\). Therefore, the total area is zero. --- **Using area, explain why** \[ \int_{0}^{\pi} \cos(\theta) \, d\theta = 0 \] **Explanation:** The function \( \cos(\theta) \) from \( 0 \) to \( \pi \) has equal positive and negative areas. \( \cos(\theta) \) is positive over \([0, \frac{\pi}{2}]\) and negative over \([\frac{\pi}{2}, \pi]\). These areas are equal in magnitude, thus cancel out, making the integral zero. --- **Using area, explain why** \[ \int_{0}^{2} (t+5)(t-3) \, dt < 0 \] **Explanation:** First, expand the expression: \[ (t+5)(t-3) = t^2 - 3t
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