Question

prove that the sum all three angles of a triangle is 180.​

Answer 1

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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 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=180

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

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Answer 2

Step-by-step explanation:

In order to prove that the sum of angles of a triangle is 180, you must know the theorems of angles of a triangle. We know that, alternate interior angles are of equal magnitude. ... Now we have to substitute the angles. ∠PAB + ∠BAC + ∠CAQ = 180°.