Can two angles in a triangle be supplementary?It's geography, angles in a triangle.

In any triangle, the sum of the 3 angles is 180 degree or
2 right angles. That is if A,Band C are the vertices of the triange,
then

angle A+B+C =180 degree or 2 right
angles.

If And B are supplementary, then A+B =180 degree.
 So C = 0.

This is a case, when AB is a line segment and
 the  expected side from A and  and the line from B wont meet at any finite distance ,or
are parallel, or meet at a distance infinitely away at C.. So there is no regular
triangle formation with the condition given.