Question

the sum of all angles of triangle is 180 degree to prove ​

Answer 1

Given: ∆Abc with 3 angles namely angles 1 ,2,3.

RTP: angle1+2+3=180degrees..

Construction: draw a line parallel to BC passing through vertex B..... Name the Angles formed as 4 and 5(in figure)

Proof: angle1 =4-----(I)

2=5(corresponding angles are equal)

-----(II)

4+3+5=180(straight line)-----(III)

Substitute I and II in III

we get. 1+2+3=180

hence proved