Law of Sines Pre-Test

A support beam needs to be placed at a [tex]28^{\circ}[/tex] angle of elevation so that the top meets a vertical beam 1.6 meters above the horizontal floor. The vertical beam meets the floor at a [tex]90^{\circ}[/tex] angle.

Law of Sines: [tex]\frac{\sin (A)}{a}=\frac{\sin (B)}{b}=\frac{\sin (C)}{c}[/tex]

Approximately how far from the vertical beam should the lower end of the support beam be placed along the horizontal floor?

A. 3.0 meters
B. 3.4 meters
C. 3.9 meters
D. 4.4 meters



Answer :

To solve this problem, we need to calculate the horizontal distance from the vertical beam to where the lower end of the support beam should be placed. Here's a step-by-step solution:

1. Understand the Problem:
- We have a support beam placed at a [tex]\(28^\circ\)[/tex] angle of elevation.
- The top of this beam meets a vertical beam 1.6 meters above the horizontal floor.
- We need to find the horizontal distance from the vertical beam to the lower end of the support beam.

2. Visualize the Scenario:
- Imagine a right-angled triangle where:
- The vertical beam represents the opposite side (1.6 meters).
- The support beam represents the hypotenuse.
- The horizontal floor distance we need to find represents the adjacent side.
- Given the angle of elevation ([tex]\(28^\circ\)[/tex]), we can use trigonometric ratios to find the horizontal distance.

3. Trigonometric Relationship:
- We use the tangent function, which relates the opposite side and the adjacent side of a right-angled triangle:
[tex]\[ \tan(\theta) = \frac{\text{opposite}}{\text{adjacent}} \][/tex]
- Here, [tex]\(\theta = 28^\circ\)[/tex] and the opposite side is 1.6 meters. We solve for the adjacent side (horizontal distance).

4. Calculate the Horizontal Distance:
- Rearrange the tangent function to solve for the adjacent side (horizontal distance):
[tex]\[ \text{adjacent} = \frac{\text{opposite}}{\tan(\theta)} \][/tex]
[tex]\[ \text{adjacent} = \frac{1.6}{\tan(28^\circ)} \][/tex]
- Calculating [tex]\(\tan(28^\circ)\)[/tex] in radians:
[tex]\[ \theta \text{ in radians} = 28^\circ \times \frac{\pi}{180} \approx 0.489 \text{ radians} \][/tex]
- From the previously obtained true result, we find:
[tex]\[ \tan(0.489) \approx 0.5317 \][/tex]
- Now substitute:
[tex]\[ \text{adjacent} = \frac{1.6}{0.5317} \approx 3.009 \text{ meters} \][/tex]

5. Match with Given Choices:
- The closest value to [tex]\(3.009\)[/tex] meters within the provided choices (3.0 meters, 3.4 meters, 3.9 meters, 4.4 meters) is:
[tex]\[ \boxed{3.0 \text{ meters}} \][/tex]

Thus, the lower end of the support beam should be placed approximately 3.0 meters away from the vertical beam along the horizontal floor.