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Chapter 2: Lines And Angles > Figure it out

Figure it out

Infinitely Many Lines Through One Point

**Observe:** The red point P is the **{.m-red}center point** through which all lines pass.

Notice how **every line** passes through point P, no matter what direction it takes!

Watch the **{.m-yellow}yellow line** rotate around point P. As it spins, it represents just a tiny fraction of the infinite lines possible.

**Key Concept:** Through any single point, there are **infinitely many** different lines that can be drawn. Each line has a different slope (direction), but they all pass through the same point.

**Lines drawn:** 4

**Rotation angle:**

Fundamental Property of Lines: Through any two distinct points, there exists exactly one unique line.

Interactive Demonstration

Instructions: Drag the red point A and blue point B to different positions and observe what happens to the line.

Key Observations:

  • No matter where you place points A and B, there is always exactly one line that passes through both points
  • This line is unique - no other line can pass through the same two points
  • When the points are moved, the line automatically adjusts to maintain this property
  • If the points coincide (same position), infinitely many lines would pass through that single point

Try This Challenge

Move the points so they are:

  1. Very close together - notice the line still exists and is unique
  2. Far apart - the line extends infinitely in both directions
  3. Arranged vertically - observe how the line becomes vertical
  4. Arranged horizontally - see how the line becomes horizontal

Remember: In each case, there is still exactly one unique line through the two points!

Rihan marked a point on a piece of paper. How many lines can he draw that pass through the point?

Sheetal marked two points on a piece of paper. How many different lines can she draw that pass through both of the points?

Instruction

Can you help Rihan and Sheetal find their answers?
Rihan can draw line(s) while Sheetal can draw line(s).
We have found the answers.

2. Name the line segments in the given below figure. Which of the five marked points are on exactly one of the line segments? Which are on two of the line segments?

Instruction

In the given figure, the line segments are: , , ,
Points on Exactly One Line Segment: and
Points on Two Line Segments:

3. Name the rays shown in the figure. Is T the starting point of each of these rays?

Instruction

The figure consists of two rays: (starting from T and extending through A) and (starting from T and extending through B)
Is T the Starting Point of Each Ray?
Yes, T is the starting point of both rays:TA and TB. Since rays have fixed endpoint and extend infinitely in one direction, is the fixed endpoint for both.

4. Draw a rough figure and write labels appropriately to illustrate each of the following:

a. OP and OQ meet at O.

b. XY and PQ intersect at point M.

c. Line l contains points E and F but not point D.

d. Point P lies on AB.

5. In the figure, name:

Instruction

(a) Five points: , , , and (Enter the answer alphabetically)
(b) A line:
(c) Four rays: , , and
(d) Five line segments: , , , and
We have found the answer.

6. Here is a ray OA. It starts at O and passes through the point A. It also passes through the point B.

Instruction

(a) Can you also name it as OB ? Why?
Yes, since is also a point lying on the ray.
(b) Can we write OA as AO? Why or why not?
No, as is the starting point of the ray.