That calculated time can be used in solving a spherical triangle. Girard also showed how the area of a spherical triangle depends on its interior angles. It can be obtained from consideration of a spherical triangle dual to the given one. In the transepts are three-light windows with a spherical triangle window above. Additional decorative elements can be implemented, such as foliation or the "spherical triangle". A spherical triangle is a geodesic triangle on the sphere. Three planes define a spherical triangle, the principal subject of this article. A Schwarz triangle is a spherical triangle that can be used to tile a sphere.