The surface area of a cone is given by the formula S = arV2 + h?, where r is the radius of the base and h is its height. Use this formula to find the number of square feet of waterproof cloth used to make the umbrella. (Assume h = 3 and r = 9.) exact answer S = ft2 approximation S = ft2

Algebra and Trigonometry (6th Edition)
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ISBN:9780134463216
Author:Robert F. Blitzer
Publisher:Robert F. Blitzer
ChapterP: Prerequisites: Fundamental Concepts Of Algebra
Section: Chapter Questions
Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
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**Calculating the Surface Area of a Cone**

In this exercise, we will determine the surface area of an umbrella modeled as a cone. First, we will give the exact answer expressed as a simplified radical expression. Then, we will provide an approximation rounded to the nearest tenth.

### Formula:
The surface area \( S \) of a cone is given by the formula:
\[ S = \pi r \sqrt{r^2 + h^2} \]
where \( r \) is the radius of the base, and \( h \) is the height.

### Given:
- Radius, \( r = 9 \) feet
- Height, \( h = 3 \) feet

### Steps to Find the Surface Area:

1. **Exact Answer:**

   Substitute the given values into the formula:
   \[ S = \pi \times 9 \times \sqrt{9^2 + 3^2} \]
   \[ S = \pi \times 9 \times \sqrt{81 + 9} \]
   \[ S = \pi \times 9 \times \sqrt{90} \]

   Simplify the radical if possible. Since \(\sqrt{90} = \sqrt{9 \times 10} = 3\sqrt{10}\), we have:
   \[ S = \pi \times 9 \times 3\sqrt{10} \]
   \[ S = 27\pi\sqrt{10} \]

   Thus, the exact surface area, \( S \), in a simplified radical form is:
   \[ S = 27\pi\sqrt{10} \ \text{ft}^2 \]

2. **Approximate Answer:**

   To find an approximation, use the approximate value of \(\pi\) and the square root:
   \[ S = 27 \times 3.14159 \times \sqrt{10} \]
   \[ S = 27 \times 3.14159 \times 3.16228 \]

   Multiply these values:
   \[ S \approx 268.8 \ \text{ft}^2 \]

### Diagram:

The provided diagram shows a cone representing an opened umbrella. The height \( h \) is labeled as 3 feet, and the radius \( r \) of the circular base is labeled as 9 feet. This
Transcribed Image Text:**Calculating the Surface Area of a Cone** In this exercise, we will determine the surface area of an umbrella modeled as a cone. First, we will give the exact answer expressed as a simplified radical expression. Then, we will provide an approximation rounded to the nearest tenth. ### Formula: The surface area \( S \) of a cone is given by the formula: \[ S = \pi r \sqrt{r^2 + h^2} \] where \( r \) is the radius of the base, and \( h \) is the height. ### Given: - Radius, \( r = 9 \) feet - Height, \( h = 3 \) feet ### Steps to Find the Surface Area: 1. **Exact Answer:** Substitute the given values into the formula: \[ S = \pi \times 9 \times \sqrt{9^2 + 3^2} \] \[ S = \pi \times 9 \times \sqrt{81 + 9} \] \[ S = \pi \times 9 \times \sqrt{90} \] Simplify the radical if possible. Since \(\sqrt{90} = \sqrt{9 \times 10} = 3\sqrt{10}\), we have: \[ S = \pi \times 9 \times 3\sqrt{10} \] \[ S = 27\pi\sqrt{10} \] Thus, the exact surface area, \( S \), in a simplified radical form is: \[ S = 27\pi\sqrt{10} \ \text{ft}^2 \] 2. **Approximate Answer:** To find an approximation, use the approximate value of \(\pi\) and the square root: \[ S = 27 \times 3.14159 \times \sqrt{10} \] \[ S = 27 \times 3.14159 \times 3.16228 \] Multiply these values: \[ S \approx 268.8 \ \text{ft}^2 \] ### Diagram: The provided diagram shows a cone representing an opened umbrella. The height \( h \) is labeled as 3 feet, and the radius \( r \) of the circular base is labeled as 9 feet. This
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