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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.

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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