You use right triangle trig here. You have the angle of 71 degrees, which is the base angle that is NOT the right angle. The length of the beam serves as our hypotenuse. The sin ratio calls for SOH...sin = side opposite over hypotenuse, right? So set it like this: sin 71 = x / 24, where x is the leg that is NOT the base. Make sure your calculator is in degree mode and multiply both sides by 24 to get an equation that looks like this: 24 sin 71 = x. Do the multiplication to get that x = 22.69 ft