Interior angles in a triangle add up to 180˚. Triangles close triangleA polygon with three straight sides. have three sides, therefore they have three angles. Interior angles in a triangle sum to a ...

Earlier today I set you these mind-mangling puzzles about non-Euclidean geometry, in which the internal angles of triangles do not add up to 180 degrees. 1. Right, Right, Right. Assume the Earth is a ...