Le linee coniugate
The study of the gears is based on the conjugated geometries according to which two curves or two surfaces in mutual movement maintain in constant contact. The geometric theory of the gears until the end of the nineteenth century was one of many branches of the applications of descriptive geometry. The study is based on knowledge of the main properties of plane curves and humps and their derivatives. The specificity of the theme is that these geometries when have to relate with their conjugated, must meet the constraints that would otherwise not have.