My first question, can a triangle have three angles, 0-180-0, and appear as a line segment with a point in the middle having no altitude?
Also, can a single dot on a piece of paper represent an infinite straight line in aspect to the dot being 3-d, extending through the paper?
There are certain "undefined terms" in geometry. A point and a line are two of them. They can only be described. A point has no dimensions. It simply represents "location". A line has only length. Abstract, at best. That's why we call them undefined.
A triangle is defined as 3 segments connecting 3 non-collinear points. So a straight line fails that definition.