An observer (o) spots a bird flying at a 55° angle from a line drawn horizontal to its nest. if the distance from the observer (o) to the bird (b) is 15,000 ft., how far is the bird (b) from its nest (n)?

Build a right triangle where the horizontal distance from the observer to the nest is the adjacent leg, the angle is 55° and the distance from the observer to the bird (inside the nest) is the hypotenuse of the triangle, which is sthe unknown variable, x.

Then, cos(55°) = adjacent leg/hypotenuse = 15,000 ft / x⇒ x = 15,000 ft / cos(55°) = 26,152 ft
 

The variables should add up to equal 1