Solid angle of its faces is one-sixth of that, or sr. Solid angles can also be measured in square degrees (1 sr = () square degrees), in square minutes and square seconds, or in fractions of the sphere (1 sr = fractional area), also known as spat (1 sp = 4 sr). In spherical coordinates there is a formula for the differential, where is the colatitude (angle from the North pole) and is the longitude. The solid angle for an arbitrary oriented surface S subtended at a point P is equal to the solid angle of the projection of the surface S
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