A sphere with arcs and poles. "The distance of all points in the circumference of a circle of a sphere…

"Every section of a sphere made by a plane is a circle."

Illustration of a sphere generated by the revolution of a semicircle ACB about its diameter AB as an…

Illustration of a sphere with a tangent plane. "A plane perpendicular to a radius at its extremity is…

Illustration of a sphere with a tangent plane. "A plane perpendicular to a radius at its extremity is…

Illustration of a sphere with a polyhedral angle whose vertex is at the center of the sphere and whose…

A sphere with quadrants and poles. "A point on the surface of a sphere, which is at the distance of…

Illustration of equal spheres with equilateral and equiangular triangles.

Illustration of two intersecting spheres. "The intersection of two spherical surfaces is the circumference…