Question

prove that sum of all angles of a triangle is 180.

Answer 1

draw a ED passing through A Parallel to BC.

Angle 3 is equal to Angle 5.(Alternative Angles)

Angle 4 is equal to Angle 4. (Alternative Angles)

Also from XY.
Angle2+ Angle1+Angle4=180° (Linear pair)

Angle1+Angle2+Angle3=180°(From 1 and 2)

Hence sum of Angles of triangle are 180°.

Answer 2

Hi friend..
Here is your answer



➡️➡️➡️➡️SOLUTION⬅️⬅️⬅️⬅️


To prove this we are given a triangle PQR and Angle 1, Angle 2 and Angle 3 are the angles of triangle PQR.

To prove Angle 1 + A angle 2 + Angle 3 = 180 degree, draw a line XYP parallel to QR through the opposite vertex P.

XPY is a line,

Therefore, Angle 4 + Angle 1 + angle 5 = 180 degree                              (1)

XPY || QR and PQ,PR are transvesals 

Angle 4 = Angle 2   &

Angle 5 = Angle 3 ( Pairs of alternate angles)

Substituting Anggle 4 and Angle 5 in (1) we get

Angle 2 + Angle 1 + Angle 3 = 180 dgree  

i.e. Angle 1 + Angle 2 + Angle 3 = 180 degree


I hope it will help
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