Prove that the sum of the angles of atriangle is 180º.

1.	Prove that the sum of the angles of atriangle is 180º.
Answer» ONG>Step-by-step explanation: 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 .......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=180o Thus, the SUM of three angles of a triangle is 180o.

Answer» ONG>Step-by-step explanation:

Given :

A triangle ABC.

∠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 .......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=180o

Thus, the SUM of three angles of a triangle is 180o.

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