Define Pressure on an Inclined Plane
Similar to a vertical plane, fluid pressure increases linearly with increasing depth. The average pressure on an inclined plane occurs at the average vertical depth. If angle σ is provided along with inclined dimensions measured from the fluid surface to the top of the inclined plane (h3), and from the fluid surface to the bottom of the inclined plane (h4), use trigonometry to determine the vertical dimensions (h1) and (h2)
Average P = ½ (ϒ) (h1+h2)
Average P = ½ (ϒ) (h3+h4) sin σ