# Questions about triangles and lines

• September 20th 2008, 01:06 PM
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?
• September 20th 2008, 01:50 PM
bkarpuz
Quote:

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?

up to me you are right in both ;)
but if the angles are allowed to be $0$ in your triangle definition.
• September 20th 2008, 02:35 PM
courteous
Quote:

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?

Deriving from both, such dot can also be a triangle.(Happy)
• September 20th 2008, 04:59 PM
masters
Quote:

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.