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Translations. Lesson 9-8. Translations. Translations are used on the coordinate plane. A translation is a shift or movement of a figure a given number of places on the coordinate plane. EXAMPLE. Suppose we have parallelogram ABCD as shown on the graph. We can “translate” this shape
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Translations Lesson 9-8
Translations • Translations are used on the coordinate plane. • A translation is a shift or movement of a figure a given number of places on the coordinate plane.
EXAMPLE Suppose we have parallelogram ABCD as shown on the graph. We can “translate” this shape 5 units to the right and 3 units down. The new image would look like this: A B C D
Notice that the entire new image Is shifted 5 units to the right and 3 units down. The labels of the image are noted with a prime ‘ symbol. A B A’ B’ C D C’ D’
TRY THIS Translate triangle QRS 4 units to The left and 5 units up. Q R S
TRY THIS Q’ Translate triangle QRS 4 units to The left and 5 units up. R’ Q S’ R S
Symmetry and Reflections Lesson 9-9
Reflection is a mirror image of a figure. • In geometry, reflectional symmetry occurs when one half of a figure is a mirror image of the other half. • The line of symmetry is the line that divides a figure into two congruent halves.
Symmetry • Notice that one half of the pentagon is the mirror image of the other. Line of symmetry
Try This • Which of the following figures have reflectional symmetry?
Try This • Which of the following figures have reflectional symmetry? YES NO YES YES YES
Symmetry • Many figures have more than one line of symmetry. Notice that the square has 4 lines of symmetry.
Try This • Draw all the lines of symmetry for the following figures.
Try This • Draw all the lines of symmetry for the following figures.
Try This • Draw all the lines of symmetry for the following figures.
Try This • Draw all the lines of symmetry for the following figures.
Try This • Draw all the lines of symmetry for the following figures.
Try This • Draw all the lines of symmetry for the following figures.
Reflections • Reflections can also be used on the coordinate plane. • A reflection is a figure that has been flipped over a line of reflection.
EXAMPLE Suppose that line segment AB is graphed as shown. If it is reflected over the y-axis, it would look like this: A B
EXAMPLE Notice that the image of the line segment is a mirror image of the original one. It is as if the paper were folded on the y-axis and it left an identical imprint on the other side of the axis. A A’ B B’
Try This Graph the image of triangle DEF after a reflection over the x-axis. D E F
Try This D E F F’ E’ D’
Try This Now graph the image of parallelogram ABCD after it is reflected over x = 2 A B C D
Try This Line of reflection A B B’ A’ C D D’ C’ Notice that the line of reflection is x = 2. It is as if the paper were folded on the line x = 2.