Answer: The answer is 381.85 feet.
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

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

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.
72.5+32.7= 105.2
Triangle angles have to equal 180
180-105.2= 74.8
Third angle= 74.8 degrees
<span>(2.3 x 10^-3)(3 x 10^8)
=(</span>2.3 x 3)(10^-3 x 10^8)
= 6.9 x 10^5
hope it helps