An alternative proof of sum of angles in a triangle; different to the one on this channel made about five years ago; linked below. Sum of angles in a triangle is 180 degrees proof #1: Chapters: 0:00 why another proof? 0:31 setting up the basic proof structure 1:11 the strategy we'll use 3:09 determining the composite angles at the top of the triangle 5:19 finding the sum of all the angles. Subscribe to TinyMaths here: