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 wet film thickness is also 100 µm. Then after complete drying of the paint, the DFT will be 100 µm because no solvent will be evaporated. This is an important concept when using paint industrially to calculate the cost of painting. It can be said that it is the real volume of paint. Here is the formula by which one can calculate the volume solid of paint, In earlier days, the volume solid was measured by a disc method but now a sophisticated instrument is also available which takes only a drop of paint to check the volume solid. Volume