If the angle at the top of the tower is known, a surveyor would use the a0 function9 to find the length x. The cosine of a 50° angle is a1 this represents the value created when length a2 is divided by a3 feet. If the angle near the top of the tower was changed to 60°, the cosine would be 0.5; now the length of x would be a4 feet. If the angle near the top of the tower was changed to 60°, the angle from the light and the ground would be a5 degrees.