Converting a plane into a Converting a plane into a Cartesian plane Cartesian plane

1. Construct two real number lines perpendicular to each 0 other at the point of each

. line• Label this point of

intersection as O for.Origin

• This divides the plan , into four quadrants

labeled QI, QII, QIII andQIV.

2. The horizontal number line - .is called the x axis

3. The vertical number line is - .called the y axis

OO X-axisX-axis

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QIIQII

(Left Arrow then left click to start animation.)(Left Arrow then left click to start animation.)

Converting a plane into a Converting a plane into a Cartesian plane Cartesian plane

4. A grid is formed from the whole numbers on each

.number line5. , 1-1 Thus establishing a

mapping between the points in the plane and ordered pairs of real ( , )numbers x y

• - X coordinate is often called the abscissa

• - Y coordinate is often called the ordinate

OO

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QIIQII At the beginning, you will only be working with whole numbers to make the learning easier. However, all ordered pairs of real numbers are valid values.Notice the point labeled A.To determine the ordered pair of real numbers that is mapped to this point see below. (Left Click to see animation.)(Left Arrow / Left Click to rerun.)

To find the coordinates of a To find the coordinates of a.point.point

1. Draw a line from the point perpendicular to the x-axis.The point where the line intersects the x-axis is the x-coordinate.

2. Draw a line from the point perpendicular to the y-axis.The point where the line intersects the y-axis is the y-coordinate.

(6, 4)(6, 4)

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Using the procedure shown on the previous page find the coordinates for each point highlighted in QI.(Left click to see the lines drawn.)(Left click again to see the coordinates.) (2, 8)

(4, 3)

(11, 5)

(14, 11)

(9, 13)

What do you notice about the What do you notice about the coordinators of all these points in coordinators of all these points in QI? QI? (Left click to see the answer.)(Left click to see the answer.)

The coordinators have positive The coordinators have positive values. All points in Q1 always values. All points in Q1 always have positive values for their have positive values for their x-coordinate and y-coordinate.x-coordinate and y-coordinate.

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Find the coordinates for each point highlighted.(Left click to see the lines drawn.)(Left click again to see the answer.)(Left click to continue.)

(6, -11)

(10, -6)

(3, -3)

(-1, -9)(-10, -7)

(-3, -2)

(-5, 4)

(-9, 8)

(-12, 11)

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Write three rules that describes the numbers that make up the x- and y-coordinates for points in QII, QIII and QIV?(Left Click to see the answers.)

(6, -11)

(10, -6)

(3, -3)

(-1, -9)(-10, -7)

(-3, -2)

(-5, 4)

(-9, 8)

(-12, 11)

All points in QIV have x-All points in QIV have x-coordinates that are positive coordinates that are positive and y-coordinates that are and y-coordinates that are negative.negative.

All points in All points in QIII have QIII have x-x-coordinates coordinates that are that are negative negative and y-and y-coordinates coordinates that are that are negative.negative.

All points in All points in QII have QII have x-x-coordinates coordinates that are that are negative negative and y-and y-coordinates coordinates that are that are positive.positive.

Left click to continue.Left click to continue.

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QIIQIIx < 0 and y > 0x < 0 and y > 0

x < 0 and y < 0x < 0 and y < 0 x >0 and y < 0x >0 and y < 0

x > 0 and y > 0x > 0 and y > 0

Give the coordinates of the points plotted on this graph. (Left click for the coordinates`.)

To which quadrant, if any, does these points belong?(Left click on the answer.)

(0, -4)

(0, -9)

(11, 0)(3, 0)

(0, 1)

(0, 5)

(-7, 0)(-14, 0)

Points on the x-axis have a y-coordinate of 0.Points on the y-axis have a x-coordinate of 0.So, points on either axes belong to no quadrant.(Left click to continue.)

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QIIQIIx < 0 and y > 0x < 0 and y > 0

x < 0 and y < 0x < 0 and y < 0 x >0 and y < 0x >0 and y < 0

x < 0 and y > 0x < 0 and y > 0The Cartesian plane is composed of six sets of points: QI, QII, QIII, QIV, x-axis, and y-axis. Therefore, the x-axis and y-axis are not part of any quadrant.(Left click to continue.)

The sets do not have any points in common, except for 1 point that is in two of the sets. What point is that?(Left click to see the answer.)(Left click to mark important information.)(Left click to continue.)

The Origin The Origin

If you are confident that you know this material, you may press the spacebar to continue. To review the material again left click on this text.

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Now, we turn our attention to plotting the graph of a ordered pair of coordinates.Plot the graph of the point (7, 9).To find this point. (Remember the ordered pair is (x, y), so 7 is the

x-coordinate and 9 is the y-coordinate.) Starting at the origin go right (positive direction) 7 units on the x-axis. From this point go up (positive direction)9 units along the grid line.Mark the point and label (First left click shows the animation.)

(Left click again to continue.)

(7, 9)

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graph of a ordered pair of coordinates.Plot the graph of the point (-4, 6).To find this point. (Remember x<0 and y>0, so the point will be in QII.) Starting at the origin go left (negative direction) 4 units on the x-axis. From this point go up (positive direction)6 units along the grid line.Mark the point and label (First left click shows the animation.) (Left click again to continue.)

(-4, 6)

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Plot the graph of the point (9, -9).(Since x>0 and y<0 the point is in QIV.) Starting at the origin go right (positive direction) 9 units on the x-axis. From this point go down (negative direction) 9 units along the grid line.Mark the point and label (First left click shows the animation.) (Left click again to continue.)

(9, -9)

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Plot the graph of the point (-10, -5).(Since x<0 and y<0 the point is in QIII.) Starting at the origin go left (negative direction) 10 units on the x-axis. From this point go down (negative direction) 5 units along the grid line.Mark the point and label (First left click shows the animation.) (Left click again to continue.)

(-10, -5)

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Plot the point having coordinates (6, -5). (First left click shows the animation.) (Left click again for next one.)

(6, -5)

Plot the point having coordinates (-4, -5). (First left click shows the animation.) (Left click again for next one.)

(-4, -5)

Plot the point having coordinates (8, 8). (First left click shows the animation.) (Left click again for next one.)

(8, 8)

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If you are confident that you know this material, left click to exit. Or, you can click on this text to repeat this part.