Spherical trigonometry
![Eight spherical triangles defined by the intersection of three great circles.](/Images/godic/202502/12/Spherical_trigonometry_Intersecting_circles.svg4130.png")
![The basic triangle on a unit sphere.](/Images/godic/202502/12/Spherical_trigonometry_basic_triangle.svg4130.png")
![The polar triangle A'B'C'](/Images/godic/202502/12/Spherical_trigonometry_polar_triangle.svg4130.png")
![](/Images/godic/202502/12/Spherical_trigonometry_vectors.svg4130.png")
Spherical trigonometry is the branch of spherical geometry that deals with the relationships between trigonometric functions of the sides and angles of the spherical polygons (especially spherical triangles) defined by a number of intersecting great circles on the sphere. Spherical trigonometry is of great importance for calculations in astronomy, geodesy and navigation.