For the water tower problem...
Draw two triangles. One starting from the ground and going to the boy's head. The other should contain the first triangle, but should continue to the top of the water tower. The angle between the base of the triangles and the hypotenuse should be 62.
Look at the smaller triangle first. Since the boy is 5 ft tall, the height is 5. The angle is 62. The tangent of the angle is equal to the height / base. Solve for the base of the smaller triangle.
Now you know the base of the larger triangle (base of smaller + 40 ft)
Use tangent again to solve for the height of the large triangle.
Hope this helps - if it doesn't I can draw a picture just post.