In this video, we state and prove the Exterior Angle Theorem as a theorem of congruence geometry, which says every exterior angle to a triangle is larger than its two remote interior angles.
This is part 17 (2/2) of the lecture series offered by Dr. Andrew Misseldine for the course Math 3130 - Modern Geometries at Southern Utah University. A transcript of this lecture can be found at Dr. Misseldine's website or through his Google Drive at:
https://drive.google.com/file/d/1rkl70_QxT23e7MqMObNEQNo4S7u-iYU7/view
This lecture is loosely based upon Section 3.3 of Roads to Geometry by Wallace and West. Please post any questions you might have below in the comment field and Dr. Misseldine (or other commenters) can answer them for you. Please also subscribe for further updates.
