Answer:
Part A)
About 74.2°.
Part B)
About 21 feet.
Step-by-step explanation:
A 22 feet ladder is leaning against a building, where the base of the ladder is six feet from the base of the building.
This is shown in the diagram below (not to scale).
Part A)
We want to determine the angle of elevation of the ladder. That is, we want to find the value of θ.
Since we know the values adjacent to θ and the hypotenuse, we can use the cosine ratio. Recall that:
[tex]\displaystyle \cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}}[/tex]
The adjacent is 6 and the hypotenuse is 22. Thus:
[tex]\displaystyle \cos \theta = \frac{6}{22} = \frac{3}{11}[/tex]
Take the inverse cosine of both sides:
[tex]\displaystyle \theta = \cos^{-1}\frac{3}{11}[/tex]
Use a calculator. Hence:
[tex]\displaystyle \theta = 74.1733...\approx 74.2^\circ[/tex]
The angle of elevation is approximately 74.2°
Part B)
We want to find how high up the ladder reaches on the building. In other words, we want to find x.
Since x is opposite to θ and we know the adjacent side, we can use the tangent ratio. Recall that:
[tex]\displaystyle \tan \theta = \frac{\text{opposite}}{\text{adjacent}}[/tex]
The opposite side is x and the adjacent side is 6. The angle θ is cos⁻¹(3/11) (we use the exact form to prevent rounding errors). Thus:
[tex]\displaystyle \tan \left(\cos^{-1}\frac{3}{11}\right) = \frac{x}{6}[/tex]
Solve for x:
[tex]\displaystyle x = 6 \tan \left(\cos^{-1}\frac{3}{11}\right)[/tex]
Use a calculator. Hence:
[tex]x = 21.1660... \approx 21\text{ feet}[/tex]
The ladder reaches about 21 feet up the building.
