SOLUTION: Prove that the sum of all angles of a triangle is 180'.

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Question 983743: Prove that the sum of all angles of a triangle is 180'.
Answer by rothauserc(4718) About Me  (Show Source):
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draw a line parallel to the base of your triangle, note that the other two sides of the triangle are transversal's intersecting the base and the parallel line which touches the top of the triangle. Since alternate angles of a transversal are equal, angles A+B+C = 180 degrees