If the side of a triangle is extended, the angle formed outside the triangle is the exterior angle. \(g\) is the interior angle. \(h\) is the exterior angle. \(g + h = 180^\circ\) The interior ...

If the side of a triangle is extended, the angle formed outside the triangle is the exterior angle. \(g\) is the interior angle. \(h\) is the exterior angle. \(g + h = 180^\circ\) The interior ...

In this space, the triangles are drawn as straight lines, so the sum of the angles is 180 degrees. It is difficult to visualize a flat universe, and it is easier to understand by capturing from a ...