9.01 Points, lines and rays
Are you ready?
Do you remember how to identify features of shapes?
How many edges does each shape have?
Learn
A single position in space is called a point. It has no size - no length and no width - and we represent a point by drawing a small dot.
A point
If we take two different points and fill in all of the space directly between them with points, we get a line segment. A line segment has a length, but no width.
A line segment
If we start with only one point, then choose a direction and fill in all of the space in that direction with points, we get a ray.
A ray
Two rays that go in opposite directions are called opposite rays. If we have two opposite rays which share the same endpoint, together they form a line.
A line
Some pairs of lines get special names. Two lines which go in the same direction and never cross each other are called parallel lines. We show that two lines are perpendicular with matching arrow markings on the lines.
A pair of parallel lines
Another special pair of lines happen when two lines form a right angle where they cross. This type of pair of lines are called perpendicular lines.
A pair of perpendicular lines
Apply
Question 1
Select the diagram showing a pair of parallel lines:
A
B
C
D
Line segments, rays, and lines are all different:
- line segments end at a point on both sides
- rays have one endpoint, and stretch forever in the other direction
- lines stretch forever in both directions
Parallel and perpendicular lines are different too:
- parallel lines go in the same direction and never cross
- perpendicular lines create a right angle where they cross