Mathematics Grade 8 15 min

Translations: graph the image

Translations: graph the image

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1

Introduction & Learning Objectives

Learning Objectives Define and identify a translation as a rigid motion. Describe a translation using coordinate notation (x,y) -> (x+a, y+b). Graph the image of a point after a given translation. Graph the image of a polygon after a given translation. Determine the translation rule given a pre-image and its image. Understand that translations preserve shape, size, and orientation, resulting in congruent figures. Have you ever slid a piece of furniture across a room without turning or flipping it? 🛋️ That's a translation in real life! In this lesson, you'll learn how to move geometric shapes on a coordinate plane without changing their size or orientation. We'll explore how to graph these 'slides' and describe them using mathematical rules, which...
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Key Concepts & Vocabulary

TermDefinitionExample TranslationA transformation that 'slides' a figure from one position to another without turning it or flipping it. Every point of the figure moves the same distance in the same direction.Sliding a triangle 3 units to the right and 2 units up. Pre-imageThe original figure before a transformation is applied. It is usually denoted by capital letters (e.g., A, B, C).If you start with triangle ABC, then ABC is the pre-image. ImageThe new figure formed after a transformation has been applied to the pre-image. It is denoted with prime notation (e.g., A', B', C').After translating triangle ABC, the new triangle A'B'C' is the image. Translation VectorA directed line segment that describes the direction and distance of a translation. It...
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Core Formulas

Coordinate Rule for Translation $(x, y) \rightarrow (x+a, y+b)$ To translate a point $(x, y)$ by 'a' units horizontally and 'b' units vertically, add 'a' to the x-coordinate and 'b' to the y-coordinate. 'a' is positive for right, negative for left. 'b' is positive for up, negative for down. Translation Vector Notation $ \langle a, b \rangle $ A translation can be described by a vector $\langle a, b \rangle$, where 'a' represents the horizontal shift and 'b' represents the vertical shift. This vector is applied to each point $(x, y)$ as $(x+a, y+b)$.

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Sample Practice Questions

Challenging
A square has vertex A at (-1, 2) and its diagonally opposite vertex C at (3, -2). The square is translated so that the image of vertex A is at the origin (0, 0). Where is the image of vertex C?
A.(2, -4)
B.(4, -4)
C.(3, -2)
D.(2, 0)
Challenging
Triangle ABC is translated to A'B'C'. The coordinates of A are (2, 5) and the coordinates of its image A' are (0, 8). The coordinates of C are (-1, 0). What are the coordinates of the midpoint of the segment B'C', if B is at (4,1)?
A.(0.5, 5.5)
B.(1, 4)
C.(-0.5, 3.5)
D.(2.5, 2)
Challenging
A line segment with endpoints J and K is translated by the vector <-3, 5>. The image segment J'K' has a midpoint at M'(0, 0). If the length of the original segment JK was 10 units, which of the following could be the coordinates of J?
A.(0, 0)
B.(-3, 5)
C.(3, -5)
D.(0, -1)

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