28
Good question. This is an 'analogue' of this puzzle: "Eight people meet for the first time. If they each shake hands with everyone else, how many handshakes are there?" There is a formula, but who would remember it?
Imagine you and I are both among the eight people. You would shake hands with seven others. I would say the same thing, and so could each of the others.
That gives 8x7 = 56, but you and I both counted the time we shook hands with one another , in fact each handshake is counted twice. The number of handshakes is actually 56/2 = 28.
This can be generalized to say that the number of ways to choose 2 objects from a group of n objects is n(n-1)/2.
Two intersecting lines can always cover three non-collinear points.
Any three non-collinear points will define a single plane. A plane is composed of an infinite number of distinct lines.
Three
the lines which are not parallel to each other are non collinear lines
Infinitely many. There are infinitely many points in the plane and although any pair of points define a line, no matter how many lines you are given, it is always possible to find a point that is not on any of them - that is, a point that is not collinear.
Two intersecting lines can always cover three non-collinear points.
Any three non-collinear points will define a single plane. A plane is composed of an infinite number of distinct lines.
Three
3
The definition of a non-collinear line is that this is a line on which points do not lie on one line. The opposite of this is a collinear point. Collinear points refer to three points that do fall on a straight line.
3 lines and one plane
they are points that aren't on the same line
Collinear pointsPoints that lie on the same line are called collinear points. If there is no line on which all of the points lie, then they are non collinear points.
the lines which are not parallel to each other are non collinear lines
Infinitely many. There are infinitely many points in the plane and although any pair of points define a line, no matter how many lines you are given, it is always possible to find a point that is not on any of them - that is, a point that is not collinear.
Definition for collinear and non collinearPoints that lie on the same line are called collinear points. If there is no line on which all of the points lie, then they are non collinear points.
Collinear pointsPoints that lie on the same line are called collinear points. If there is no line on which all of the points lie, then they are non collinear points.