Why is the sum of the angles of a triangle always 180 degrees?
It’s quite simple to prove. Draw 2 parallel lines with the base of the triangle at the line on the bottom and the tip of the triangle touching the top line. You can then extend the sides and use the fact that alternate angles are congruent with a transversal (the sides) and two parallel lines to show that the angles of the triangle add up to the total angle measure of the top line (which is 180°). So the sum of the angles of a triangle would be 180°. QED Here is a nice visual of the proof: http://www.mathsrevision.net/gcse/pages.… I hope this helps!
