Reflect Points Across Axes

6.NOS.7 · Unit 9 · Lesson 7

Name   Period

Objectives / Objetivos

Content Objective: I can reflect points across the x-axis and y-axis on the coordinate plane.

Language Objective: I can explain my work using the words reflection, x-axis, y-axis, and symmetry.

Key Idea / Idea clave

Reflect over the x-axis: the y-coordinate changes sign. Reflect over the y-axis: the x-coordinate changes sign.

I Notice / Observo

  • When (2, 4) reflects over the x-axis to (2, -4), which coordinate changed?
  • When (5, 3) reflects over the y-axis to (-5, 3), which coordinate changed?

I Wonder / Me pregunto

  • What happens if you reflect a point over BOTH axes?

Vocabulary / Vocabulario

Term / TérminoDefinition / Definición
Reflection
Reflexión		A flipped, mirror image across a line.
Una imagen reflejada al otro lado de una línea.
x-axis
Eje x		The line that goes across the grid. Flipping over it changes the y sign.
La línea que va de lado en la cuadrícula. Voltear sobre ella cambia el signo de y.
y-axis
Eje y		The line that goes up the grid. Flipping over it changes the x sign.
La línea que va hacia arriba en la cuadrícula. Voltear sobre ella cambia el signo de x.
Symmetry
Simetría		When a shape looks the same on both sides of a line.
Cuando una figura se ve igual a ambos lados de una línea.
Integer
Número entero		Whole numbers and their opposites, like -2, -1, 0, 1, 2.
Números enteros y sus opuestos, como -2, -1, 0, 1, 2.

Practice Preview / Vista previa de práctica

  1. What is the reflection of (4, -3) over the x-axis?
    1. (-4, -3)
    2. (4, 3)
    3. (-4, 3)
    4. (3, -4)
  2. Plot (1, 4) and its reflections: over the x-axis, over the y-axis, and over both axes
  3. Find the reflection of each point over the given axis.
  4. Find the Reflection Error
    1. Step 1: Problem — Reflect (-3, 5) over the y-axis
    2. Step 2: Student thinking — The y-axis is vertical, so I change the y-coordinate
    3. Step 3: Student answer — (-3, -5)

    Which step has the mistake? Explain it and write the correct work.

Reflection / Reflexión

One thing I learned today / Una cosa que aprendí hoy: