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GeoGebraGeoGebra Classroom

Exterior Angle Inequality Theorem

The Exterior Angle and the Interior angles

We consider the relationship of the Exterior angle with the two interior angles of the triangle. Move the Green and Red Sliders to compare the measures of the Green angle and the Red angle with the Blue angle.

Exterior Angle Inequality Theorem

The measure of any exterior angle of a triangle is greater than either of the opposite interior angles.