A 25-foot ladder stands against a vertical wall at an angle of n degrees with the ground. If sin n = 4 / 5, how far is the base of the ladder from the wall?

A. 12
B. 13
C. 14
D. 15
E. 16

1 answer

Sin n = 4 / 5. Remember that the formula for sin would be Opposite / Hypotenuse. So:

Sin n = Opposite / Hypotenuse = 4 / 5
Sine n = Opposite / 25 = 4 / 5
5 Opposite = 100
5 / 5 Opposite = 100 / 5
Opposite = 20.

Now what we do is use Pythagorean Theorem to find the length of the adjacent side.

a^2 + b^2 = c^2
20^2 + b^2 = 25^2
400 + b^2 = 625
400 - 400 + b^2 = 625 - 400
b^2 = 225
sqrt(b^2) = sqrt(225)
b = 15.
Answer choice D