Explore the relationship between the sum of the two remote interior angles and the exterior angle of the third angle in a triangle by dragging sliders and making observations.

Drag the two sliders to transform the angle measures for angle A and B of the triangle. Compare the sum of these angles to the exterior angle at C in the triangle. Is this true for any triangle ABC?[br][br]1. What is the sum of the interior and exterior angles formed at point C in the triangle?[br]2. Create an acute triangle by dragging vertex A to the right. What is the sum of angle A and B? What is the measure of the exterior angle at point C?[br]3. Create an obtuse triangle. What is the sum of angle A and B? What is the measure of the exterior angle at point C?[br]4. What do you notice about the relationship between the two remote interior angles of a triangle and the exterior angle of the third angle of a triangle?[br]Turn on the check box "show relationship" to check your statement.