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 why the sum of three sides of a triangle is 180 degree?

Hi Devisha!
 
If your question is “Why the sum of three angles of a triangle is 180 degree?”, then the answer to this question is as given below.
 
Let us we are given a triangle PQR and ∠1, ∠2 and ∠3 are the angles of Δ PQR (figure shown below). We need to prove that ∠1 + ∠2 + ∠3 = 180°.
 
 
We use the properties related to parallel lines to prove this. For this, let us draw a line XPY parallel to QR through the opposite vertex P, as shown in the figure given below
 
 
Now, XPY is a line.
Therefore, ∠4 + ∠1 + ∠5 = 180°  … (1)
But XPY || QR and PQ, PR are transversals.
So, ∠4 = ∠2 and ∠5 = ∠3 (Pairs of alternate angles)
Substituting ∠4 and ∠5 in (1), we get
∠2 + ∠1 + ∠3 = 180°
That is, ∠1 + ∠2 + ∠3 = 180°
 
Cheers!

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 you are wrong.sum of three angles is 180 degrees

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because that's all the degrees that three sides of any length put together (a triangle) can hold- any less and it wouldnt even be a polygon, and any more and it would have to have more sides.
 
 
some more detail
 
A triangle has three angles. The angle sum property of a triangle defines that the sum of the three angles is always 180º

 

Proof:

   Let us see about the angle sum property of the triangle.

 

   Here the base of the triangle has been extended and we get an exterior angle d which is adjacent to the interior angle c. As the sum of an interior angle and its adjacent exterior angle is 180º, c + d = 180º.

  The exterior angle of a triangle is equal to the sum of the two opposite interior angles.

 

   Thus, We get c + d = 180º

  c + a + b = 180º

  a + b + c = 180º.

  So the sum of three angles of a triangle is 180º. In any triangle ABC, the sum of the three triangles which can be given as

  ∠A + ∠B +∠C = 180º.

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thankssssss

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