Points and lines

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)

Activity

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.