Question

19 180
Polove that the sum
of angle of a triangle​

Answer 1

A triangle ABC.

To prove :

∠A+∠B+∠C=180°

⟹∠1+∠2+∠3=180°

Construction :

Through A, draw a line l parallel to BC.

Proof :

Since l∥BC. Therefore,

∠2=∠4

And, ∠3=∠5

adding eq(i)and(ii)

Therefore, ∠2+∠3=∠4+∠5

∠1+∠2+∠3=∠1+∠4+∠5 [adding∠1bothSide]

∠1+∠2+∠3=180°

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