The angles inside a shape are called interior angles. If the side of a triangle is extended, the angle formed outside the triangle is the exterior angle.

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 ...

Set squares are drawing instruments used to create vertical, horizontal, and diagonal lines as well as certain angles. They may be shaped as squares, Ls, or triangles, although in American usage set ...