The plot below shows a visual representation of the properties mentioned above, namely that the interior and exterior angles of the triangle add to 180 and 360 degrees respectively.
Choose either interior angles or exterior angles. Drag the red point to change the angles of the triangle and move the slider from left to right to see the proofs in motion.
Interior Angles: The interior angles form a semi-circle (180 degrees).
Exterior Angles: The exterior angles form a full circle (360 degrees).