The height of the pole is the vertical leg of the right triangle. The angle of depression is an exterior angle to the triangle at its upper angle. The angle of depression is complementary to the interior angle, so the measure of the interior angle is 15. The base angles are 90 and 75. Use the tangent ratio now, using the base angle of 75 and the height of the pole being 50: tan75=50/x.
Make sure your calculator is in degree mode to do this and get that x = 13.4
