Here, you know the angle between the Adjacent side and the hypotenuse. You also know the length of the Adjacent side. You need to know the length of the Opposite side (the side opposite the angle you know). So you're dealing with the Tangent ratio, O/A. Get hold of a trigonometric table or a calculator with trig functions, and see what the tangent ratio is for an angle of 38°. Plug in the 43 feet (the length of the Adjacent side) and figure the length of the Opposite side using the tangent ratio you found.