Why is it impossible for a triangle to contain a 180 degree angle?

By definition, a triangle must have three angles. It is also known that the interior angles of a triangle must total 180 degrees. If a triangle contained a single interior angle of 180 degrees, the other angles of the supposed triangle would both have to be zero, and the supposed triangle would be a straight line.

Triangles have 3 angles.

All of the interior angles must add up to 180 degrees


If 1 of them was 180 degrees, the other 2 angles would have to equal 0 degrees, in which case, it would just be a line.