Question

prove that the sum of the angles of a triangles is 180​

Answer 1

Given: A triangle ABC

To prove: Angle A + Angle B + Angle C = 180

Construction: Draw a line parellel to side BC passing through A and name it XY

Proof: We know that angle on a straight line is 180 degrees.

So, angle YAC + angle XAB + angle BAC = 180 degrees -------(1)

Now, angle YAC = angle BCA (alternate angles) ----(2)

Similarly, angle XAB = angle ABC (alternate angles) -----(3)

Substituting values from (2) and (3) in (1)

angle BAC + angle BCA + angle ABC = 180 degrees

Hence proved

Answer 2

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