Question

show that the sum of interior angle in triangle is 180​

Answer 1

Answer:

Given :

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 ll BC. Therefore,

∠2=∠4 .......eq(i)

And, ∠3=∠5......eq(ii)

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°

Answer 2

Answer:

∆abc

60 at each corner

so that angle at a 60⁰

angle at b 60⁰

angle at c 60⁰