2. Introduction
to Lines
A line is infinite and straight. If you look at
the picture above, is a line, is also
a line and is a line. A line is identified
when you name two points on the line and
draw a line over the letters. A line is
a set of continuous points that extend
indefinitely in either of its direction. Lines
are also named with lowercase letters or a
single lower case letter. For instance, I
could name one of the lines above simply by
indicating an e.
3. Lines
There are SEVEN types of
LINES:
Line segment
Ray
Horizontal line
Vertical line
Parallel line
Intersecting line
Perpendicular line
4. lines
1.A line segment is a straight line segment which
is part of the straight line between two
points. To identify a line segment, one can write
AB or . The points on each side of the line
segment are referred to as the end points.
5. A ray is the part of the line which consists of the
given point and the set of all points on one side of
the end point.
A is the end point and this ray
means that all points starting from A are included in
in the ray. A ray can also be written like:
6. A horizontal line is one the goes left-to-right, parallel to
the x-axis of the coordinate plane. All points on the line
will have the same y-coordinate. In the figure above, drag
either point and note that the line is horizontal when they
both have the same y-coordinate.
A horizontal line has a slope of zero. As you move to the
right along the line, it does not rise or fall at all. As you
drag the points above, you can see that when the line is
horizontal, the points both have the same y-coordinate,
and the slope is zero.
7. In geometry, a vertical line is one which runs from up
and down the page. Its cousin is the horizontal line
which runs left to right horizontal line. across the
page. A vertical line is perpendicular to a horizontal
line
8. Parallel lines
Parallel lines remain the
same distance apart over
their entire length. No
matter how far you
extend them, they will
never meet.
9. Intersecting lines
• If two lines in the same plane are not
parallel, they will intersect at a common
point. Those lines are intersecting lines.
10. Perpendicula
r lines
• Perpendicular means "at right angles". A line
meeting another at a right angle, or 90° is said to
be perpendicular to it. In the figure above, the
line AB is perpendicular to the line DF. If they
met at some other angle we would say that AB
meets DF 'obliquely'. Move the point A around
and create both situations. Move the mouse
carefully to get AB exactly perpendicular to DF
A
F
D
B
11. Two rays that share the same endpoint form an angle. The point where the
rays intersect is called the vertex of the angle. The two rays are called the
sides of the angle.
We can specify an angle by using a point on each ray and the vertex. The
angle below may be specified as angle ABC or as angle CBA; you may also
see this written as ABC or as CBA.
12. There are SIX types of
ANGLES:
Right angle
Obtuse angle
Acute angle
Straight angle
Reflex angle
Full angle
