"An angle that forms a linear pair with one of the interior angle the triangle" is the best definition of an exterior angle of a triangle.
<u>Option: C</u>
<u>Explanation:</u>
When to the sum of the inward angles opposite outer angle of a triangle the sum of the inward angles opposite is equivalent thus understood as exterior angle of a triangle.
The Triangle outer angle theorem for more about is if at each vertex the equivalent angle is drawn, the outer angles always add up to 360°. In reality, this is valid for any convex polygon, not just triangles.
In the most easiest pattern , since any angle of triangle equivalent is 60′, the outer angle would be 120′. Therefore all exterior angles sum is:
120 + 120 + 120 = 360°.
The answer to you question is
1/81
