Question

C 2) Write given and to prove of statment the sum of measure of all angle of triangle is 180°
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Answer 1

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=180

o

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

o