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Cartesian coordinate system



A Cartesian coordinate system, also known as rectangular coordinate system, can be used to plot points and graph lines.

The following is an example of rectangular coordinate system


coordinate-system-image

It is basically, a set of two number lines

The horizontal line is called x-axis and the vertical line is called y-axis

A good real life example of a vertical number line or y-axis is a thermometer.

Notice that it has 4 quadrants.

In quadrant I, x and y are positive

In quadrant II, x is negative, but y is positive

In quadrant III, x and y are negative

In quadrant IV, x is positive, but y is negative

The center, or intersection of the two axis is equal to (0,0)

In this lesson, you will learn to plot points on the cartesian coordinate system.

A point is represented by a pair of numbers (x, y)

x stands for any value on the x-axis and y stands for any value on the y-axis

An example of a point is (1, 5)

Let us now plot some points.

Locate point (2,3).

x = 2 and y = 3

Draw a vertical line at x = 2 and draw a horizontal line at y = 3

Where the two lines meet or intersect, is your point (in red)

coordinate-system-image

Locate point (-3, 1)

Draw a vertical line at x = -3 and draw a horizontal line at y = 1

The intersection of the two lines is your point

coordinate-system-image

Locate point (-4, -4)

Draw a vertical line at x = -4 and draw a horizontal line at y = -4

coordinate-system-image

Tricky cases are when points are located on the x-axis or the y-axis.

Students usually get confused, so study the following two examples carefully

Locate point (2,0)

Draw a vertical line at x = 2 and draw a horizontal line at y = 0.

Notice that when y = 0, your horizontal line is on the x-axis

Important point to remember:

When y = 0, your point is always located on the x-axis

coordinate-system-image

Locate point (0, -3)

Draw a vertical line at x = 0 and draw a horizontal line at y = -3.

Notice that when x = 0, your vertical line is on the x-axis

Important point to remember:

When x = 0, your point is always located on the y-axis

coordinate-system-image

Other examples:

coordinate-system-image






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