Angles of Triangles and Parallel Lines

I introduce the theorem that state the interior sum of the angles of a triangle add up to 180 degrees and show how this is true with parallel lines. The second theorem I cover explains how an exterior angle of a triangle is equal to the sum of the 2 interior remote angles. EXAMPLES at 6:34 9:00 14:46 19:43 23:32 Find free review test, useful notes and more at http://www.mathplane.com/ If you'd like to make a donation to support my efforts look for the "Tip the Teacher" button on my channel's homepage    / profrobbob