Is the diagram I have what you mean?.
If so, we can use similar triangles:
You did not state your weight density of the fluid. You can put that in.
A triangular plate with height 4 ft and a base of 5 ft is submerged vertically in water so that the top is 2 ft below the surface. Express the hydrostatic force against one side of the plate as an integral and evaluate it. (Give your answer correct to the nearest whole number.)
Thanks! I don't know what to do at all, by the way, all I know is that I need the area and pressure. There's a picture of it of a triangle suspended in a square, and the hypotenuse side is facing the lower right.