Why do angles inside a triangle add to 180 degrees?

Answer 1

The angles inside a triangle add up to 180 degrees due to the properties of parallel lines and transversals. When a triangle is drawn, if you extend one side and draw a line parallel to the opposite side, the alternate interior angles formed are equal to the triangle's angles. The three angles of the triangle, along with the two corresponding angles created by the parallel line, together form a straight line, which measures 180 degrees. Thus, the sum of the triangle's angles must also equal 180 degrees.