Flag semaphore is a way to use flags to signal messages. The diagrams show how to signal the letters Z and J in the semaphore alphabet. For each, precisely describe a rotation that would take the left-hand flag (L) to the right-hand flag (R).
Z
J
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13.2
Activity
Turning on a Grid
Quadrilateral A B C D and points R and Q plotted on square grid. Point R is one unit to the left of Point A. Point Q is one unit below Point A. A B and C D are both 3 units long.
Rotate 90 degrees clockwise around .
Rotate 180 degrees around .
Rotate 120 degrees clockwise around .
Rotate 60 degrees counterclockwise around .
Quadrilateral H J K L M N and Points P and O on an isometric grid. Points O and P are below and to the right of the Quadrilateral. Points O, N and K are on the same diagonal grid line. Points M, L and P are on the same vertical grid line.
13.3
Activity
Translate, Rotate, Reflect
Mai suspects triangle is congruent to triangle . She thinks these steps will work to show that there is a rigid transformation from to .
Translate by directed line segment .
Rotate the image degrees clockwise around point .
Reflect that image over line .
Draw each image, and determine the angle of rotation needed for these steps to take to .
Student Lesson Summary
The three rigid motions are reflect, translate, and rotate. Each of these rigid motions can be applied to any figure to create an image that is congruent. To do a rotation, we need to know three things: the center, the direction, and the angle.
Rotate 90 degrees clockwise around point .
Rotate 120 degrees counterclockwise around point .
Glossary
None
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