Question

Prove that the sum of three angles of a tringle is 180°​

Answer 1

Answer:

Given :

A triangle ABC.

To prove :

∠A+∠B+∠C=180  

o

⟹∠1+∠2+∠3=180  

o

 

Construction :

Through A, draw a line l parallel to BC.

Proof :

Since l∥BC. Therefore,

∠2=∠4(i)

And, ∠3=∠5(ii)

adding(i)and(ii)

Therefore, ∠2+∠3=∠4+∠5

∠1+∠2+∠3=∠1+∠4+∠5  [adding∠1 both Side]

∠1+∠2+∠3=180 o

 

Thus, the sum of three angles of a triangle is 180  o

Hope it helps! :):)