Prove that the sum of the three angles of a triangle is 180 degree.

Asked by Aravindh Ramesh | 29th Jun, 2013, 05:03: PM

Expert Answer:

Consider a triangle ABC. 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'.
It is obvious that <)B'CA + <)ACB + <)BCA' = 180 degrees.
Thus <)ABC + <)BCA + <)CAB = 180 degrees.

Answered by  | 29th Jun, 2013, 05:14: PM

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