A water tank is constructed from a cylinder. For most water tanks, the cylinder is upright. For ours, the cylinder is horizontal. It is easy for us to measure the depth of the water in the tank with a simple gauge. We want to be able to determine the volume.
We can simplify this problem, and simply worry about a circle. Suppose a circle of known radius R is standing in water of depth H. What is the area A of the wet portion of the circle? That is, what is a formula for A in terms of H and R?
To do this problem, you will need trigonometry!
I give up, show me the solution.