The Cartesian PLaneThe Cartesian PLaneLet’s start graphing!Let’s start graphing!

Introduction to x-y plane

You learned about the basic (counting) number line back in elementary school:

Later on, you were introduced to zero and negatives, which completed the number line:

Descartes' breakthrough was in taking a second number line, standing it up on its end, and crossing the first number line at zero:

Ordered PairsAn 'ordered pair' is simply two numbers in a certain order. For example, the numbers '2' and '3' can form two ordered pairs:

2, 3       and      3, 2

In mathematics, we use two numbers to accurately locate a position on a rectangular grid, like this:

Coordinate system

On a graph grid, the point (0,0) is called the 'origin'

The first coordinate of a plotted point is called the 'x' coordinate

The second coordinate of a plotted point is called the 'y' coordinate

originorigin

X X coordinatecoordinate

y y coordinatecoordinate

Let’s Graph

(2, 4) ●

(-4, 3) ●

(-5, -4) ●

(3, -3) ●

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12

3 4

(2, 4)(-4, 3)

(-5, -4) (3, -3)

Your turn: which quadrant will the point lie?

12

3 4

(2, -3)

(-2, -1)

(5, -5)

(-2, 1)

(1, 5)

2

3

4

1

4

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