Question

what is the answer for the set of shapes in which the sum of all interior angles is 180​

Answer 1

Answer:

Proof that the sum of the angles in a triangle is 180 degrees. If ABC is a triangle then <)ABC + <)BCA + <)CAB = 180 degrees. Draw line a through points A and B. Draw line b through point C and parallel to line a. Since lines a and b are parallel, <)BAC = <)B'CA and <)ABC = <)BCA'.