Surface of revolution never negative, the area is given by If the curve is described by the function , , then the integral becomes for revolution around the -axis, and for revolution around the "y"-axis (using ). These come from the above formula. For example, the spherical surface with unit radius is generated by the curve , , when ranges over . Its area is therefore For the case of the spherical curve with radius , rotated about the -axis A minimal surface of revolution is the surface of revolution of the curve between two given points which minimizes surface area. A basic
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