4.2. Exterior Angles Theorems http://www.ck12.org
4.2 Exterior Angles Theorems
Here you’ll learn what an exterior angle is as well as two theorems involving exterior angles: that the sum of the
exterior angles is always 360◦and that in a triangle, an exterior angle is equal to the sum of its remote interior angles.
What if you knew that two of the exterior angles of a triangle measured 130◦? How could you find the measure of
the third exterior angle? After completing this Concept, you’ll be able to apply the Exterior Angle Sum Theorem to
solve problems like this one.
Watch This
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Click image to the left for more content.CK-12 Foundation: Chapter4ExteriorAnglesTheoremsA
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Click image to the left for more content.James Sousa:Introduction totheExterior Anglesof a Triangle
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Click image to the left for more content.James Sousa:Proof that the Sum of the Exterior Angles of a Triangleis 360 Degrees
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Click image to the left for more content.James Sousa:Proof of the Exterior Angles Theorem