A lighthouse, L, is on an island 8 mi away from the closest point, P, on the beach. If the lighthouse light rotates clockwise at a constant rate of 19 revolutions/min, how fast (in mi/min) does the beam of light move across the beach 4 mi away from the closest point on the beach?

Holt Mcdougal Larson Pre-algebra: Student Edition 2012
1st Edition
ISBN:9780547587776
Author:HOLT MCDOUGAL
Publisher:HOLT MCDOUGAL
Chapter12: Angle Relationships And Transformations
Section12.5: Reflections And Symmetry
Problem 20E
Question

A lighthouse, L, is on an island 8 mi away from the closest point, P, on the beach. If the lighthouse light rotates clockwise at a constant rate of 19 revolutions/min, how fast (in mi/min) does the beam of light move across the beach 4 mi away from the closest point on the beach?

 

=___________    (mi/min

### Understanding Distance and Geometry

#### Description of the Diagram:

The diagram presents a visual representation of a right-angled triangle formed by two locations: point **L** on an island and point **P** on the mainland.

#### Key Elements:

1. **Triangle Components**:
   - The hypotenuse of the triangle extends from point **P** on the mainland directly to point **L** on the island, and it measures 8 miles.
   - One leg of the right triangle runs horizontally from point **P** for 4 miles.
   - The other leg extends vertically from the end of the 4-mile leg to point **L** on the island, representing the direct distance across the water.

2. **Points & Distance**:
   - **Point L** represents the location of interest on the island.
   - **Point P** represents the starting point on the mainland.
   - The direct distance across the water from the mainland at point **P** to the island at point **L** is 8 miles.
   - The horizontal distance from point **P** inland is 4 miles.

#### Mathematical Example:

The diagram is an excellent illustration of the Pythagorean theorem, which is fundamental in geometry for calculating distances and understanding the relationships between the sides of right-angled triangles. According to the Pythagorean theorem:

\[ \text{Hypotenuse}^2 = \text{Base}^2 + \text{Perpendicular}^2 \]

Using the values provided:
- Hypotenuse (\(c\)) = 8 miles
- Base (\(b\)) = 4 miles

We can calculate the Perpendicular (\(a\)):
\[ 8^2 = 4^2 + a^2 \]
\[ 64 = 16 + a^2 \]
\[ a^2 = 64 - 16 \]
\[ a^2 = 48 \]
\[ a = \sqrt{48} \approx 6.93 \text{ miles}\]

Thus, the vertical distance across the water is approximately 6.93 miles.
Transcribed Image Text:### Understanding Distance and Geometry #### Description of the Diagram: The diagram presents a visual representation of a right-angled triangle formed by two locations: point **L** on an island and point **P** on the mainland. #### Key Elements: 1. **Triangle Components**: - The hypotenuse of the triangle extends from point **P** on the mainland directly to point **L** on the island, and it measures 8 miles. - One leg of the right triangle runs horizontally from point **P** for 4 miles. - The other leg extends vertically from the end of the 4-mile leg to point **L** on the island, representing the direct distance across the water. 2. **Points & Distance**: - **Point L** represents the location of interest on the island. - **Point P** represents the starting point on the mainland. - The direct distance across the water from the mainland at point **P** to the island at point **L** is 8 miles. - The horizontal distance from point **P** inland is 4 miles. #### Mathematical Example: The diagram is an excellent illustration of the Pythagorean theorem, which is fundamental in geometry for calculating distances and understanding the relationships between the sides of right-angled triangles. According to the Pythagorean theorem: \[ \text{Hypotenuse}^2 = \text{Base}^2 + \text{Perpendicular}^2 \] Using the values provided: - Hypotenuse (\(c\)) = 8 miles - Base (\(b\)) = 4 miles We can calculate the Perpendicular (\(a\)): \[ 8^2 = 4^2 + a^2 \] \[ 64 = 16 + a^2 \] \[ a^2 = 64 - 16 \] \[ a^2 = 48 \] \[ a = \sqrt{48} \approx 6.93 \text{ miles}\] Thus, the vertical distance across the water is approximately 6.93 miles.
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