Question

How to proof that sum of all angle is = 180​

Answer 1

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to prove:- angle 1 + angle 2 + angle 3 =180°

construction:- draw PQ passing through a such that PQ||BC

angle 4 = angle 2 (alternate interior angles)...(i)

angle 5 = angle 3 (alternate interior angles)...(ii)

As PQ is a straight line,

angle 1 + angle 4 + angle 5 = 180°...(iii)

putting equation (i) and (ii) in (iii)

angle 1 + angle 2 + angle 3 = 180°

P.T.O.

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