Co-interior angles are two angles on the same side of the transversal. They are the inside or interior angles and their sums add to 180[math]^\circ[/math]. Use the two animations below to explore and test this angle relationship. Additionally, in the first animation, drag around the point "A" to manipulate the drawing.

Co-exterior angles are very similar to co-interior angles. They are both on the same side of the transversal but they are both on the outside or exterior. Like co-interior angles, they both add up to 1[math]^\circ[/math].