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.

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The other is vertical, with up being the positive direction and down being the negative

direction.

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5

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The origin is the point where the

two number lines meet.

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The two number lines have special

names.

The horizontal number line is

called the x-axis.

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The vertical number line is

called the y-axis.

y

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The plural of axis is axes. We often

talk about the coordinate axes.

y

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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,

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yCoordinates written in

parentheses are called an ordered pair.

yx,

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Consider the point which has coordinates,

(4, -2)

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The first number tells you how far

to move to the side.

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So the 4 in (4, -2) says we need to move 4 units to

the right.

Remember to start at the origin.

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The second number tells you how far to move

up or down.

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The –2 in (4, -2) tells you to move down two units.

2,4

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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)

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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

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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