Find angle between guy-wires using difference formula for tangent

In this math example, we are given a situation where two guy wires are attached to a vertical pole at different heights but the same distance from the base of the wall. We find the angle created between the two guy wires by using the difference formula for tangent.

For a climbing wall, a guy-wire R is attached 47 feet high on a vertical pole. Added support is provided by another guy-wire S attached 40 feet above the ground on the same pole. If the wires are attached to the ground 50 feet from the pole, find the angle (alpha) between the wires.