Solid angle orientation formula_9, and distance from the viewer as: where the surface area of a sphere is . The solid angle of a cone with its apex at the apex of the solid angle, and with apex angle 2, is the area of a spherical cap on a unit sphere For small such that , this reduces to the area of a circle . The above is found by computing the following double integral using the unit surface element in spherical coordinates: This formula can also be derived without the use of calculus. Over 2200 years ago Archimedes proved that the
Volume solid Volume solid Volume solid is the volume of paint after it has dried. Paint contains solvent, resin, pigments and additives. After applying the paint, the solid portion will be left on the substrate. Volume solid is the term which indicates the proportion of the solid contacting the paint on a volume basis. For example, if paint is applied in a wet film at a 100 µm thickness, and the volume solid of paint is 50%, then the dry film thickness will be 50 µm as 50% of the wet paint has evaporated. Suppose the volume solid is 100%, and the