Lesson Topic: Symmetry in the Coordinate Plane

Lesson Objective: I can…Locate reflections of coordinate

points across both axes on the coordinate plane using the x-

axis and/or y-axis as the line of symmetry.

Preview of Exit Ticket1. Start at (-5, 2). Reflect across the x-axis. What point do you end up at?2. Start at (-5, 2). Reflect across the y-axis. What point do you end up at?Challenge: Come up with a starting

point and a set of directions to navigate to an ending point, including

at least one reflection. Be sure to include what the ending point is.

Opening Exercise

Give an example of two opposite numbers and

describe where the numbers lie on the number

line. How are opposite numbers similar and how

are they different?

Exercise, continued…

1. When the coordinates of two points are ( , ) and (− , ), 𝑥 𝑦 𝑥 𝑦what line of symmetry do the

points share? Explain.2. When the coordinates of two

points are ( , ) and ( ,− ), 𝑥 𝑦 𝑥 𝑦what line of symmetry do the

points share? Explain.

Let’s Sum it Up…

Answer the following questions in complete sentences:

What does a reflection of a point across a line of symmetry on the coordinate plane

look like?How do we find the ordered pair of a point

reflected across an axis?Why is this important to know how to do?

Example 2: Navigating the Coordinate Plane using

ReflectionsWhere are you after you follow the directions?

Begin at (7, 2). Move 3 units down, then reflect over the y-axis.

Begin at (4, -5). Reflect over the x-axis, then move 7 units down, then to the right 2 units.

Begin at (-3, 0). Reflect over the x-axis then move 6 units to the right. Move up two units, then reflect

over the x-axis again. Begin at (-2, 8). Decrease the y-coordinate by 6.

Reflect over the y-axis, then move down 3 units. Begin at (5, -1). Reflect over the x-axis, then reflect

over the y-axis.*Come up with your own starting points and directions.

Example 3: Describing How to Navigate the Coordinate Plane

Describe a sequence of directions to navigate from the starting point to the ending point. Begin at (9, -3) and end at (-4, -3). Use

exactly one reflection across an axis. Begin at (0, 0) and end at (5, -1). Use

exactly one reflection across an axis. Begin at (0, 0) and end at (-1, -6). Use

exactly two reflections across axes.*Find other sequences that would work for

each set of points above.

Lesson Summary

When the coordinates of two points differ only by one sign, such as (-8, 2) and (8,

2), what do the similarities and differences in the coordinates tell us about their relative locations on the

plane? What is the relationship between (5, 1)

and (5, -1)? Given one point, how can you locate the other?

Evaluate Your Learning4321

How will you “Sharpen Your Saw”?

Exit Ticket (on Socrative)

1. Start at (-5, 2). Reflect across the x-axis. What point do you end up at?

2. Start at (-5, 2). Reflect across the y-axis. What point do you end up at?Challenge: Come up with a starting

point and a set of directions to navigate to an ending point, including at least

one reflection. Be sure to include what the ending point is.

*When you’re done, close your iPad and get a homework worksheet.