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Lesson 28:  Introduction to Rotation

Rotation is an easy topic in geometry.  It requires a little bit of visualization, and a basic understanding of how angles in a circle are measured.  This lesson introduces you to the basic concept.

Don't forget to watch the embedded video clip for this lesson at the bottom of the page.  Please be sure to read the embedded video information and disclaimer.

Imagine a drawing like the turtle pictured below, and look at the first row.  I've turned it in a clockwise direction so that instead of pointing to the left, it is pointing up.  That is called a 90 degree clockwise rotation

A circle has 360 degrees.  This needs to be memorized.  You can see that in the first row, I rotated the turtle one-quarter (one-fourth) of a full circle.  360 ÷ 4 = 90, and that's why it's a 90 degree rotation.

Introduction to Rotation

In the second row, I also rotated the turtle 90 degrees, but this time in a counterclockwise manner.  It's still one-fourth of a circle, but I just rotated it in the opposite direction. 

In the third row, I rotated the turtle half a circle, which is 360 ÷ 2 = 180 degrees.  Make sure you understand two things:  First, it doesn't matter if you rotate the object 180 degrees clockwise or counterclockwise.  It will end up in the same position.  Also, make sure you can see that what was done is an actual rotation (a "spinning around"), as opposed to a "flipping," or what is actually called a reflection.  

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