Euclidean geometry is the study of plane and solid figures on the basis of axioms and theorems employed by the Greek mathematician Euclid. Is there such a thing as non-Euclidean geometry that can be described by different axioms? What is the sum of degrees of angles of a triangle? What’s the shortest distance between two points? Do parallel lines ever cross? Form circles and triangles on a flat, a spherical and a hyperbolic surface to discover non-Euclidean geometries like elliptic and hyperbolic. Learn about curvature and how parallel lines can intersect.