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A 14-foot ladder is leaning against a building. The ladder makes a 45-degree angle with the ground. How far up the building does the ladder reach?

A. [tex]$14 \sqrt{2}$[/tex] feet
B. 7 feet
C. [tex]$7 \sqrt{2}$[/tex] feet
D. [tex][tex]$28 \sqrt{2}$[/tex][/tex] feet


Sagot :

To determine how far up the building a 14-foot ladder reaches when it makes a 45-degree angle with the ground, we can use trigonometry.

Here’s the step-by-step solution:

1. Understand the Problem:
We have a right triangle where:
- The ladder serves as the hypotenuse ([tex]\(c\)[/tex]) of the triangle, which is 14 feet.
- The angle between the ladder and the ground is [tex]\(45^\circ\)[/tex].
- We want to find the height ([tex]\(h\)[/tex]) the ladder reaches up the building, which is the side opposite the [tex]\(45^\circ\)[/tex] angle.

2. Identify the Trigonometric Function:
The sine function relates the angle to the length of the opposite side and the hypotenuse. The sine of an angle in a right triangle is defined as:
[tex]\[ \sin(\theta) = \frac{\text{Opposite}}{\text{Hypotenuse}} \][/tex]

Here, [tex]\(\theta = 45^\circ\)[/tex], the opposite side is the height ([tex]\(h\)[/tex]), and the hypotenuse ([tex]\(c\)[/tex]) is the ladder length (14 feet).

3. Set Up the Equation:
[tex]\[ \sin(45^\circ) = \frac{h}{14} \][/tex]

4. Determine the Value of [tex]\(\sin (45^\circ)\)[/tex]:
From trigonometry, we know:
[tex]\[ \sin(45^\circ) = \frac{\sqrt{2}}{2} \][/tex]

5. Solving for the Height (h):
Substitute [tex]\(\sin (45^\circ)\)[/tex] into the equation:
[tex]\[ \frac{\sqrt{2}}{2} = \frac{h}{14} \][/tex]

To solve for [tex]\(h\)[/tex], multiply both sides of the equation by 14:
[tex]\[ h = 14 \times \frac{\sqrt{2}}{2} \][/tex]

Simplify the right-hand side:
[tex]\[ h = 14 \times \frac{\sqrt{2}}{2} = 14 \div 2 \times \sqrt{2} = 7 \sqrt{2} \][/tex]

Therefore, the height up the building that the ladder reaches is [tex]\(7\sqrt{2}\)[/tex] feet.

So, the correct answer is:
C. [tex]\(7 \sqrt{2}\)[/tex] feet