Points and lines
When we have a line, we can mark a point on the line or not on it.
‘A’ is on ‘l1’, ‘B’ is not on ‘l1’ or ‘l2’. ‘B’ may be closer or far away, but not on the both of the lines ‘l1’ and ‘l2’. However, when any two points are given, there is exactly ONE line passing through them! Take several pairs of points and verify if this is true.
What about 3 points and a line? Consider the following lines ‘l1’ ‘l2’ ‘l3’ and ‘l4’ and A,B,C be three points.
When all the three points are on a line, they are special; we call such points as collinear points.
When two lines intersect at right angles (90°), we call them as perpendicular lines. (Refer to 4.31)
A book is an object where you can see parallel, perpendicular and intersecting lines.
Suggest atleast 2 more examples having parallel, perpendicular and intersecting lines.
Two intersecting lines cut at a point. Will three lines intersect at one point? Fig.4.32 will help you to answer this.
When many lines intersect at a single point, that is again special, we call that point P as a point of concurrency. The lines are called concurrent lines.