Download Plotting on the Coordinate Plane

Plotting on the
Coordinate Plane
Lesson 4.02
After completing this lesson, you will be able to say:
•
I can identify and position pairs of rational
numbers on a coordinate plane.
Plotting Points
In order to understand how to plot points on a coordinate plane, we must first recall
how to locate integers on horizontal and vertical number line diagrams
Point R is on –7. The negative shows that the point is
7 spaces to the left of 0.
Point T is on 9. This is positive, so the point is 9
spaces to the right of 0.
Plotting Points
Let’s plot point S at 4 and point P at –5 on
a vertical number line.
Point P is on –5. The negative shows that
the point is 5 spaces below 0.
Point S is on 4. This is positive, so the
point is 4 spaces above 0.
Plotting a Point
Plot the point (3,1)
Start at the origin.
(Remember the first number tells you how
far to go left or right.)
Because the first coordinate is positive
three, you should travel three units to the
right.
The second number tells you up or down.
The second number is positive so you will
move up 1 unit
Place a dot here to mark your point.
Example
Richard’s ticket says that he is sitting at (–3, 4). Let’s find his location!
Try It!
Jen’s ticket says she is seated at (0, –2). Plot the
point to help Jen find her seat!
Check your work
Rational Numbers
Rational numbers can be integers, decimals, or fractions.
Plotting decimals and fractions on a number line is as easy as plotting any integer;
you just have to think about the values in between integers.
Let’s Plot the point (3.5, 0.5)
Plotting decimals is similar to plotting
integers. Follow the same steps:
1. Start at the origin.
2. Move 3.5 units to the right.
The 3.5 is in the middle of 3 and 4.
3. Then go up 0.5. The 0.5 is in the middle
of 0 and 1.
4. Plot the point.
Example
Doris wants to buy some cupcakes. The cupcake stand is located at (−5, 2 3/4).
Let’s help Doris figure out where it is by plotting the cupcake stand on the
coordinate plane!
Try It
Check your work
Determining the Coordinates of a Point
We need to find the coordinates of Point P
It is in the second quadrant. So we already know
that the x-coordinate will be negative and the ycoordinate will be positive.
The first number of the ordered pair is the xcoordinate. Count along the x-axis to find how
many units left of the origin the point lies. This
point is three units left of the origin. So the first
number in the ordered pair is −3.
The second number in the ordered pair is the
y-coordinate. You must find out how many units
the point is above the x-axis. Because Point P is
2 units above the x-axis, the y-coordinate is 2.
That means the coordinates of Point P are
(−3, 2)
Try It
Plot the points on the coordinate plane
A (2, 4)
B (-1/2, -3)
C (2.75, -4)
Check your work
A (2, 4)
B (-1/2, -3)
∎A
C (2.75, -4)
B
∎
∎
C
Now that you completed this lesson, you should
be able to say:
• I can identify and position pairs of rational
numbers on a coordinate plane.