Example 2

9.1.2 Example 2

Description

Quick Overview

The section illustrates how to calculate the length of a ladder required for an electrician to reach a specific height safely.

Standard

This section explains a problem involving an electrician who needs to reach a point below the top of a pole. It demonstrates how to determine the length of a ladder needed when placed at an angle and the distance at which it should be positioned from the pole using trigonometric ratios.

Detailed

Detailed Summary

In this example, an electrician must repair an electrical fault on a pole height of 5 m. The task requires her to reach a point 1.3 m below the pole's top, making the required vertical reach 3.7 m (5 m - 1.3 m). To successfully calculate the necessary length of the ladder, the problem uses right-angled triangle properties and trigonometric ratios, specifically the sine function. The length of the ladder corresponds to the hypotenuse of the triangle formed.

The sine of the angle (60°) allows us to set up the equation using the formula:

$$\frac{BD}{BC} = \sin(60°)$$
Where BD (the vertical reach) equals 3.7 m, leading to the length of the ladder, BC, being approximately 4.28 m. Additionally, to find how far from the pole the ladder's base should be placed, the cotangent function provides the necessary calculation, yielding a distance of approximately 2.14 m. This example is significant for understanding practical applications of trigonometry in real-world scenarios.

Key Concepts

  • Vertical Reach: The effective height that needs to be reached by the ladder.

  • Trigonometric Ratios: Ratios that relate the angles and sides of a triangle, essential for calculations.

  • Angle of Incline: The angle at which the ladder meets the ground, affecting the length needed.

Memory Aids

🎵 Rhymes Time

  • To climb up high and reach the sky, sin of sixty helps you fly!

📖 Fascinating Stories

  • Imagine an electrician standing before a tall pole, needing her ladder to reach just the right spot. With a quick calculation, she finds the perfect angle, making her job safe and efficient.

🧠 Other Memory Gems

  • Remember: Sine = Opposite over Hypotenuse can help us find the height when the angle is clear!

🎯 Super Acronyms

LADDER

  • Length Always Depends on Distance
  • Elevation
  • and Reach!

Examples

  • A ladder placed at a 60° angle can reach a height of 4.28 m when the vertical distance is 3.7 m.

  • For a 5 m pole, the effective distance from the base of the ladder, given certain angles, can be calculated using cotangent.

Glossary of Terms

  • Term: Trigonometry

    Definition:

    A branch of mathematics dealing with the relationships between the angles and sides of triangles.

  • Term: Sine Function

    Definition:

    A trigonometric function representing the ratio of the opposite side to the hypotenuse in a right triangle.

  • Term: Cotangent Function

    Definition:

    A trigonometric function representing the ratio of the adjacent side to the opposite side in a right triangle.

  • Term: Hypotenuse

    Definition:

    The longest side of a right triangle, opposite the right angle.