The line of sight is the hypotenuse of a right triangle with short leg 400 m, 90 degree angle where the short leg meets the ground, an 83 degree angle at the top, and a 7 degree angle across from the right angle on the ground. Because this 7 degree angle is an alternate interior angle with the angle of depression, they are the same degree measure. Looking for the hypotenuse, we use the sin ratio: sin (7) = 400/x.
