Question

prove that the sum of the angle of the triangle is 180

Answer 1

Take a Triangle ABC. Draw a parallel XY(of a fixed length) to BC through point A. The angle B = angle XAB(alternate angles). Angle C = angle YAC(alternate angles). Then you can see that XAB, A and YAC are in a straight line. And as you know sum of angles in a straight line = 180°, Sum of angles of a triangle = 180°.

Answer 2

Answer:

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