Question

prove sum of all sides of a triangle is 180 degree​

Answer 1

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Answer 2

Since the triangles are congruent each triangle has half as many degrees, namely 180. ... But if you look at the two right angles that add up to 180 degrees so the other angles, the angles of the original triangle, add up to 360 - 180 = 180 degrees

The angles in the triangle add up to 180 degrees. So a + b + y = 180. The angles on a straight line add up to 180 degrees.