# Is an equilateral triangle the same as an equiangular triangle, in any geometry?

I have heard of both equilateral triangles and equiangular triangles. (For example, this sporcle quiz lists both.) Are these always equivalent, regardless of geometry?

I know they are the same in Euclidean geometry (a triangle that is equilateral has three 60 degree angles), but how about elliptic or hyperbolic? Or geometries without constant curvature?

In elliptic and hyperbolic geometry, I believe an equilateral triangle is uniquely determined up to congruence by one of its angles, but I'm not sure of the proof.

If the conditions are equivalent for triangles, are there two words because they are also used to describe equilateral / equiangular polygons, which are not always the same? For example, a rectangle is equiangular but need not be equilateral, and a rhombus is equilateral but need not be equiangular. What's so special about triangles? (or tetrahedra?)

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If you don't have constant curvature, then all bets are off. You can make any set of angles and lengths into a geodesic triangle by bending the surface appropriately. – Henning Makholm Dec 29 '11 at 22:43