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| | 13 Theory slides |
| | 13 Exercises - Grade E - A |
| | Each lesson is meant to take 1-2 classroom sessions |
Get ready for an adventure! Discover the location of enemy ships hidden on the game board by using specific points. Each point on the board is represented by the combination of a letter and a number. Place the boats by dragging them from the stern, or the back, and rotate them by clicking on the bow, or the front.
A coordinate system is a reference framework used to describe the positions of objects like points, lines, and surfaces in a space. A fixed point called the origin is used as a reference in the coordinate system. The most common types of coordinate systems are one-, two-, or three-dimensional.
A coordinate plane, also known as a Cartesian or a rectangular coordinate system, is a two-dimensional coordinate system. It is a grid that results from intersecting a vertical number line with a horizontal number line at their zero points. The horizontal number line is usually named the x-axis and the vertical number line is usually the y-axis.
A coordinate is the position of an object in a coordinate system relative to the corresponding axis. Coordinates are often seen together with other coordinates, which can describe the position of an object in a coordinate system with one, two, three, or even more dimensions.
In a two-dimensional coordinate system, points are usually expressed as a coordinate pair — also called an ordered pair — denoted by (x,y). The first coordinate states the position along the x-axis and the second coordinate states the position along the y-axis.
Identify the coordinates of the given point. Write the coordinates as an ordered pair (x,y), where x represents the x-coordinate and y the y-coordinate.
Dominika plays basketball with her friends every afternoon. She warms up by running and picks up two friends, Jordan and Emily, on the way to the court. Dominika uses ordered pairs to represent the positions of her and her friends' houses.
| Position | |
|---|---|
| Dominika's House | D=(2,1) |
| Jordan's House | J=(2,4) |
| Emily's House | E=(-1,4) |
With this information in mind, consider the position of Dominika's house. Dominika's House D=( 2, 1) The x-coordinate is 2 and the y-coordinate is 1. Move 2 units to the right of the origin and then 1 unit up to graph Dominika's house on the coordinate plane.
Now, consider the coordinates of Jordan's and Emily's houses. Jordan's House & Emily's House J=( 2, 4)&E=( -1, 4) On the coordinate plane, move 2 units horizontally to the right of the origin and then 4 units up to graph the position of Jordan's house. To plot Emily's house, start at the origin again. Move 1 unit to the left and 4 units up to graph Emily's house.
Notice that this corresponds to graph III.
Basketball Court C=( -1, 1) Add this point to the graph from the previous part. Move 1 unit horizontally to the left of the origin and then 1 unit up.
The points can now be joined according to the given order D, J, E, F, and D. Draw a line starting from point D to point J. Next, from point J, go to point E, and so on until point C is connected to point D.
This graph matches the one given in option I.
Dominika's house is represented by the point (2,1) on a coordinate plane. Every morning, she runs to a place five blocks away from her house, then returns home using the same route.
Keeping this in mind, one route she can take is moving five blocks directly to the right. Move 5 units to the right starting her house to show this possible destination. Remember that Dominika's house is located at (2,1), not the origin!
Another spot Dominika might go is one block up and four blocks to the right of her starting point. It does not matter if she moves up on her first, second, third, fourth, or final move. Her destination will always be the same if she moves one block up out of the five total moves.
Follow the same reasoning to find the other places that Dominika can go. Plot each as ordered pairs on the coordinate plane.
Now that all the points are plotted on the graph, connect them with lines to see the overall shape.
The shape is a rotated square.
| Route from Home | Calculations | Destination |
|---|---|---|
| 5 blocks to the right | (2+ 5,1) | (7,1) |
| 4 blocks to the right and 1 block up | (2+ 4,1+ 1) | (6,2) |
| 3 blocks to the right and 2 blocks up | (2+ 3,1+ 2) | (5,3) |
| 2 blocks to the right and 3 blocks up | (2+ 2,1+ 3) | (4,4) |
| 1 block to the right and 4 blocks up | (2+ 1,1+ 4) | (3,5) |
| 5 blocks up | (2,1+ 5) | (2,6) |
| 1 block to the left and 4 blocks up | (2- 1,1+ 4) | (1,5) |
| 2 blocks to the left and 3 blocks up | (2- 2,1+ 3) | (0,4) |
| 3 blocks to the left and 2 blocks up | (2- 3,1+ 2) | (-1,3) |
| 4 blocks to the left and 1 block up | (2- 4,1+ 1) | (-2,2) |
| 5 blocks to the left | (2- 5,1) | (-3,1) |
| 4 blocks to the left and 1 block down | (2- 4,1- 1) | (-2,0) |
| 3 blocks to the left and 2 blocks down | (2- 3,1- 2) | (-1,-1) |
| 2 blocks to the left and 3 blocks down | (2- 2,1- 3) | (0,-2) |
| 1 block to the left and 4 blocks down | (2- 1,1- 4) | (1,-3) |
| 5 blocks down | (2,1- 5) | (2,-4) |
| 1 block to the right and 4 blocks down | (2+ 1,1- 4) | (3,-3) |
| 2 blocks to the right and 3 blocks down | (2+ 2,1- 3) | (4,-2) |
| 3 blocks to the right and 2 blocks down | (2+ 3,1- 2) | (5,-1) |
| 4 blocks to the right and 1 block down | (2+ 4,1- 1) | (6,0) |
In a coordinate plane, the intersection of the x-axis and the y-axis produces four regions called quadrants. The quadrants are numbered counterclockwise from the top right quadrant as Quadrant I to Quadrant IV in the bottom right.
The signs of the coordinates of a point can be determined based on which quadrant the point lies in.
Conversely, the quadrant of a point can be found by looking at the signs of its coordinates.
A coordinate system has four quadrants that provide information about the signs of the x- and y-coordinates of a point. In the following applet, identify in which quadrant the given point lies.
Dominika is drafting a logo for her basketball team to wear on their jerseys. She wants the logo to have a cool geometric shape, so she sets some points that she thinks will look good. Help her design the logo by matching each point with its corresponding quadrant on the coordinate plane.
| Point | Signs of Coordinates | Quadrant |
|---|---|---|
| ( -2, -8) | ( -, -) | Quadrant III |
| ( 4, -2) | ( +, -) | Quadrant IV |
| ( -11, 3) | ( -, +) | Quadrant II |
| ( 4, 3) | ( +, +) | Quadrant I |
Now that the quadrant of each point has been identified, plot the points on a coordinate plane. Move horizontally from the origin the number of units indicated by the x-coordinate and vertically the number of units specified by the y-coordinate of each point.
The logo is a hit, and the team gains more and more fans as a result!
Reflecting a point means making a mirror image of that point by flipping it across a certain line or axis. The following rules show how to find reflected points across a specific axis.
| Point | Axis of Reflection | Procedure | Reflected Point |
|---|---|---|---|
| (x_1,y_1) | x | Change the y-coordinate to its opposite. | (x_1,- y_1) |
| (x_1,y_1) | y | Change the x-coordinate to its opposite. | (- x_1,y_1) |
| (x_1,y_1) | x and y | Change the x- and y-coordinates to their opposites. | (- x_1,- y_1) |
Next, the process for reflecting points across the x-axis, the y-axis, or both, on a coordinate plane will be shown. Consider the points A, B, and C.
| Point | Axis of Reflection | Reflected Point |
|---|---|---|
| A = (5,8) | x | ? |
| B = (10,-5) | y | ? |
| C = (-4,-7) | x and y | ? |
There are two steps to follow to reflect a point.
Dominika's team is only one game away from winning the basketball tournament! Dominika is a shooting guard and wants to use her math skills to improve her game. She starts by figuring out the point on the court from where she usually scores using a coordinate plane. This point is (-4,-3).
Point&Reflection Acrossx-axis (-4, -3)&(-4, 3) Graph this point on the coordinate plane. Start at the origin and move 4 units to the left and 3 units up.
Dominika is interested in the mirror point of (-4, -3) because it is a great shooting position. This point is as far away from the basket as the original point but is oriented in a different direction. This can give her an advantage over her opponents and help her score more points during game!
Point&Reflection Acrossy-axis ( -4,-3)&( 4,-3) Add this point to the graph.
Now that Dominika understands her attack and defense positions better, she can perform much better on the court. Her team is doing great and they keep scoring point after point until before they know it, they win first place in the tournament. They are the champions!
This lesson showed how to locate points with respect to the x- and y-axis on a coordinate plane. A third axis, usually called the z-axis, can be used to provide more information about the position of objects. Think of it like this.
| Description | |
|---|---|
| x-axis | Tells if something is in front of or behind the origin. |
| y-axis | Tells if something is to the left or right of the origin |
| z-axis | Tells if something is above or below the origin. |
These three axes create a 3D coordinate system that is similar to the coordinate plane but with the addition of an extra dimension. This additional dimension means that points are represented as ordered triples (x,y,z) instead of as ordered pairs, as in the coordinate plane.
Diego gathered some information for his homework about Jefferson Junior High School. He surveyed some students and asked how many hours they spent studying each week. He wrote the information in a table and made a graph showing his results.
| Hours of Study per Week | Number of Students |
|---|---|
| 1 | 3 |
| 2 | 5 |
| 3 | 10 |
| 4 | 15 |
| 5 | 12 |
| 6 | 8 |
| 7 | 4 |
| 8 | 2 |
However, his dog got into his backpack pulled everything out of it. Diego must choose which of four graphs matches his data. Help him find the correct graph.
Let's make a graph for the data Diego recorded to determine the correct option. We will first write an ordered pair for each row of data from the table. The x-coordinate is the hours of study per week and the y-coordinate is the number of students.
| Hours of Study per Week, x | Number of Students, y | (x,y) |
|---|---|---|
| 1 | 3 | ( 1, 3) |
| 2 | 5 | ( 2, 5) |
| 3 | 10 | ( 3, 10) |
| 4 | 15 | ( 4, 15) |
| 5 | 12 | ( 5, 12) |
| 6 | 8 | ( 6, 8) |
| 7 | 4 | ( 7, 4) |
| 8 | 2 | ( 8, 2) |
Our graph will be in the first quadrant because the coordinates of each ordered pair are non-negative. The x-coordinate indicates how far to move on the x-axis and the y-coordinate indicates how far to move on the y-axis. Let's plot our data!
This graph corresponds to option B.
Mark wants to determine the shape formed by this set of ordered pairs. (-3, 1), (-2, 4), (1, 3), (3, 0), (2, -3), (-1, -4) Help him identify the shape that these pairs create when they are joined in the given order.
Let's plot the set of ordered pairs as points on a coordinate plane. Once we have plotted them, we can connect them to see what shape they create. Remember, in an ordered pair, the first number represents the x-coordinate and the second number represents the y-coordinate. Ordered Pair (x-coordinate,y-coordinate) The x-coordinate tells us how far to move along the x-axis and the y-coordinate tells us how far to move along the y-axis. We can move 3 units to the left from the origin and then 1 unit up to get to the point (-3, 1).
We can follow a similar process to graph the rest of the coordinate pairs.
Let's connect the points to identify the shape they create.
The shape that these points form is a six-sided figure called a hexagon.
Look at the following ordered pairs. (3,-4), (-5,6), (7,-2), (2,-8) Identify the ordered pair that does not belong with the other three.
We can examine the signs of the coordinates for each ordered pair to determine the quadrant where the point is located. First, let's review how to determine a point's quadrant based on the signs of the coordinates.
With this information in mind, let's now consider the first given ordered pair. (3,-4) Since the x-coordinate is positive and the y-coordinate is negative, we can tell that the ordered pair (3, -4) is in Quadrant IV. We can identify the quadrant for the other points by following a similar reasoning.
| Ordered Pair | Signs of the Coordinates | Quadrant |
|---|---|---|
| ( 3, -4) | ( +, -) | Quadrant IV |
| ( -5, 6) | ( -, +) | Quadrant II |
| ( 7, -2) | ( +, -) | Quadrant IV |
| ( 2, -8) | ( +, -) | Quadrant IV |
After identifying the quadrant of each ordered pair, we can see that three of them belong to Quadrant IV, but the ordered pair (-5,6) is in Quadrant II. This means that (-5,6) is the ordered pair that is different from the others.
We want to find the place located at the reflection of point ( 5, -4) across the y-axis. We can do this by keeping the y-coordinate of -4 and changing the x-coordinate 5 to its opposite -5. Point&Reflection Acrossy-axis ( 5, -4)&( -5, -4) We will move 5 units to the left from the origin and 4 units down to identify the place located at the point ( -5, -4).
This means that the place located at the reflection of (5,-4) across the y-axis is the cafeteria.
Let's begin by determining the coordinates of the gym. We can do this by drawing arrows from this point to each axis.
The arrow touches the x-axis at x= 5 and the horizontal arrow touches the y-axis at y= 3. These numbers represent the gym's coordinates. Gym's Coordinates ( 5, 3) We can now reflect this point across the x-axis. We keep its x-coordinate and switch the sign of its y-coordinate to get its reflection. Gym&Reflection Acrossx-axis ( 5, 3)&( 5, -3) Let's find the reflected point on the coordinate plane.
The science lab is located at the reflection of the gym across the x-axis.
Heichi is solving a math puzzle to find a hidden shape using a set of points on the coordinate plane. He has already identified the following points. B(1,-1), C(6,-1), E(4,-9) F(0,-5), H(-2,-3) He needs to find the missing ordered pairs which fit the following descriptions.
| Point | Description |
|---|---|
| A | Reflection of F across the x-axis. |
| D | Reflection of H across the y-axis. |
| G | Reflection of E across the y-axis. |
| I | Reflection of C across the y-axis. |
| J | Reflection of B across the y-axis. |
If Heichi connects all the points in alphabetical order, what shape will the points form?
Let's start by graphing the given points on a coordinate plane. Move left or right the number of units specified by the x-coordinate and then move up or down the number of units specified by the y-coordinate to plot each point.
Now that we have the graph of the known points, we can begin by finding the corresponding reflections to identify the missing points. Let's look at the descriptions of the unknown points.
| Point | Description |
|---|---|
| A | Reflection of F across the x-axis. |
| D | Reflection of H across the y-axis. |
| G | Reflection of E across the y-axis. |
| I | Reflection of C across the y-axis. |
| J | Reflection of B across the y-axis. |
Let's find the coordinates of point A, which is the reflection of point F across the x-axis. We keep the x-coordinate and change the y-coordinate to its opposite to reflect a point across the x-axis. For point F( 0, -5), we change its y-coordinate to 5 and keep its x-coordinate 0 the same to get the location of point A. cc Point&Reflection Acrossx-axis F( 0, -5)&A( 0, 5) We can use a similar method to find point D, which is a reflection of point H across the y-axis. We keep the y-coordinate and change the x-coordinate to its opposite to reflect a point across the y-axis. cc Point&Reflection Acrossy-axis H( -2, -3)&D( 2, -3) The rest of the unknown points can be determined following a similar fashion.
| Point | Description | Reflection |
|---|---|---|
| A | Reflection of F across the x-axis. | F( 0, -5) ⇒ A( 0, 5) |
| D | Reflection of H across the y-axis. | H( -2, -3) ⇒ D( 2, -3) |
| G | Reflection of E across the y-axis. | E( 4, -9) ⇒ G( -4, -9) |
| I | Reflection of C across the y-axis. | C( 6, -1) ⇒ I( -6, -1) |
| J | Reflection of B across the y-axis. | B( 1, -1) ⇒ J( -1, -1) |
Finally, let's add the unknown points and connect them in alphabetical order to identify the shape they form.
The points form a star, corresponding to option B.