My problem is to determine how far one can see to the horizon, depending on how far above the water the person is and to create a formula that determines the distance as a function of the height. To start with, the hypotenuse is the distance from the core to the persons eyes. (x+e). The cathetus being the distance from the core to the waterlevel (x) and the 2nd cathetus being the distance to the horizon (d). This is easily calculated with Pythagoras (x+e)^2 - (x)^2 = (d)^2. With the fact that a cathetus to a spheric object has an angle of 90degrees. How shall I proceed to create this formula?