Step-by-step explanation: Given that a window is 20 feet above the ground. From there, the angle of elevation to the top of a building across the street is 78°, and the angle of depression to the base of the same building is 15°. We are to calculate the height of the building across the street.

This situation is framed very nicely in the attached figure, where

BG = 20 feet, ∠AWB = 78°, ∠WAB = WBG = 15° and AH = height of the bulding across the street = ?

From the right-angled triangle WGB, we have

$\dfrac{WG}{WB}=\tan 15^\circ\\\\\\\Rightarrow \dfrac{20}{b}=\tan 15^\circ\\\\\\\Rightarrow b=\dfrac{20}{\tan 15^\circ},$

and from the right-angled triangle WAB, we have'

$\dfrac{AB}{WB}=\tan 78^\circ\\\\\\\Rightarrow \dfrac{h}{b}=\tan 15^\circ\\\\\\\Rightarrow h=\tan 78^\circ\times\dfrac{20}{\tan 15^\circ}\\\\\\\Rightarrow h=361.85.$

Therefore, AH = AB + BH = h + GB = 361.85+20 = 381.85 feet.

Thus, the height of the building across the street is 381.85 feet.

8 0

2 years ago

Use picture attached:

Olenka [21]

I think the answer is C.

3 0

2 years ago

Read 2 more answers

Gas station X charges $4.00 per gallon of gas. Gas station Y charges $4.12 per gallon of gas. What is the percent increase from

kirill [66]

First, find the increase in charge between the two station. That is:

$4.12-$4.00=$0.12

Then, divide the increase by the price charged by Gas Station X.

$0.12/$4.00=0.03

Lastly, since it is a decimal, transform it to percentage by multiplying 100%

0.03x100%=3%

Hope this is the brainliest answer.

3 0

2 years ago