2. The volume of a right circular cone is Irh where r is the radius of the base and h is the height of a cone. Use the disk method to derive this formula.

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Chapter1: Functions And Models
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**Volume of a Right Circular Cone**

**Problem Statement:**
The volume of a right circular cone is \(\frac{\pi r^2 h}{3}\) where \(r\) is the radius of the base and \(h\) is the height of the cone. Use the disk method to derive this formula.

**Detailed Solution:**

**Step-by-step Derivation Using Disk Method:**

1. **Understanding the Geometry:**
   - Consider a right circular cone with height \(h\) and base radius \(r\).
   - The cone is oriented such that its vertex is at the origin (0,0).

2. **Disk Method Concept:**
   - Imagine slicing the cone into very thin horizontal disks (circular slices) perpendicular to the \(y\)-axis.
   - We'll integrate these disks' volumes from the base to the apex of the cone.

3. **Equation of the Cone's Surface:**
   - At a height \(y\), the radius of the disk is proportional to \(y\), given by \(r(y) = \frac{r}{h}y\).

4. **Volume of a Thin Disk (dV):**
   - Each disk has a small thickness \(dy\) and radius \(r(y)\).
   - Volume of each disk: \(dV = \pi \left(\frac{r}{h} y \right)^2 dy\).

5. **Integrating to Find the Cone's Total Volume:**
   - Integrate \(dV\) from the base (\(y=0\)) to the top (\(y=h\)):
     \[
     V = \int_{0}^{h} \pi \left(\frac{r}{h} y \right)^2 dy
     \]

6. **Simplifying the Integral:**
   - \(V = \pi \int_{0}^{h} \left(\frac{r^2}{h^2} y^2 \right) dy\)
   - \(V = \pi \frac{r^2}{h^2} \int_{0}^{h} y^2 dy\)

7. **Evaluating the Definite Integral:**
   - The integral of \(y^2\) gives: \(\int_{0}^{h} y^2 dy = \left[ \frac{y^3}{3} \right]_{0}^{h}\
Transcribed Image Text:**Volume of a Right Circular Cone** **Problem Statement:** The volume of a right circular cone is \(\frac{\pi r^2 h}{3}\) where \(r\) is the radius of the base and \(h\) is the height of the cone. Use the disk method to derive this formula. **Detailed Solution:** **Step-by-step Derivation Using Disk Method:** 1. **Understanding the Geometry:** - Consider a right circular cone with height \(h\) and base radius \(r\). - The cone is oriented such that its vertex is at the origin (0,0). 2. **Disk Method Concept:** - Imagine slicing the cone into very thin horizontal disks (circular slices) perpendicular to the \(y\)-axis. - We'll integrate these disks' volumes from the base to the apex of the cone. 3. **Equation of the Cone's Surface:** - At a height \(y\), the radius of the disk is proportional to \(y\), given by \(r(y) = \frac{r}{h}y\). 4. **Volume of a Thin Disk (dV):** - Each disk has a small thickness \(dy\) and radius \(r(y)\). - Volume of each disk: \(dV = \pi \left(\frac{r}{h} y \right)^2 dy\). 5. **Integrating to Find the Cone's Total Volume:** - Integrate \(dV\) from the base (\(y=0\)) to the top (\(y=h\)): \[ V = \int_{0}^{h} \pi \left(\frac{r}{h} y \right)^2 dy \] 6. **Simplifying the Integral:** - \(V = \pi \int_{0}^{h} \left(\frac{r^2}{h^2} y^2 \right) dy\) - \(V = \pi \frac{r^2}{h^2} \int_{0}^{h} y^2 dy\) 7. **Evaluating the Definite Integral:** - The integral of \(y^2\) gives: \(\int_{0}^{h} y^2 dy = \left[ \frac{y^3}{3} \right]_{0}^{h}\
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