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The Coordinate Plane• Chapter 4 Section 4.1
P. 206
2,4
5,1
-5
-5
5
5
2,2 1,7
The coordinate plane is divided by two number lines. One is
horizontal, like the number line you already know.
-5 50 10-10
The other is vertical, with up being the positive direction and down being the negative
direction.
-5 50 10-10
5
-5
The origin is the point where the
two number lines meet.
-5 50 10-10
5
-5
The two number lines have special
names.
The horizontal number line is
called the x-axis.
x-5 50 10-10
5
-5
The vertical number line is
called the y-axis.
y
x-5 50 10-10
5
-5
The plural of axis is axes. We often
talk about the coordinate axes.
y
x-5 50 10-10
5
-5
To study a point, we need to know where to find it. So we give it
coordinates.
Coordinates are like an address. They tell you how you can get to a
point if you start at the origin.
yCoordinates are always written in parentheses, with the x-value first.
yx,
x-5 50 10-10
5
-5
yCoordinates written in
parentheses are called an ordered pair.
yx,
x-5 50 10-10
5
-5
Consider the point which has coordinates,
(4, -2)
-5 50 10-10
5
-5
The first number tells you how far
to move to the side.
-5 50 10-10
5
-5
So the 4 in (4, -2) says we need to move 4 units to
the right.
Remember to start at the origin.
-5 50 10-10
5
-5
The second number tells you how far to move
up or down.
-5 50 10-10
5
-5
The –2 in (4, -2) tells you to move down two units.
2,4
-5 50 10-10
5
-5
To get to the origin from the origin, we don’t
move at all.
0,0So the origin is
designated by the ordered pair,
(0, 0)
-5 50 10-10
5
-5
The two number lines divide the plane into four
regions.
In Quadrant I, all numbers are
positive.
In Quadrant III, x- and y-values are both negative.
In Quadrant IV, x-values are positive and y-values are
negative.
III
III IV
-5 50 10-10
5
-5
Give the coordinates of each point:
3,2
2,3 4,2
1,5
Tell how you can find each point:
0,4
Remember to start at the origin!
7,8
5,4 9,0 12,7
From the origin, move to the right 8 units, then down 7 units.
Use your own words to explain what each term means:
origin
coordinates
quadrant
axis
ordered pair
• Read Section 4.1 – especially about functions !!
• Assignment: P. 209 1-21
Review Vocabulary from this section