The definition states that complementary angles are any two angles whose sum is 90°. (The angles do not have to be next to each other to be complementary.) As seen in the diagram on the left, a 30° angle + a 60° angle = 90° so they are complementary angles. Notice that the two angles form a right angle or 1/4 of a circle.

If I write the word complementary and change the first letter "C" into the number nine and I think of the letter "O" as the number zero, I have a memory trick my mathematical brain can remember.

Supplementary Angles are two angles whose sum is 180°. Again, the two angles do not have to be together to be supplementary, just so long as the total is 180 degrees. In the illustration on your right, a 110° angle + a 70° angle = 180°; so, they are supplementary angles. Together, they form a straight angle or 1/2 of a circle.

Since there are so many puns for geometric terms. I have to share a bit of geometry humor. (My students endure many geometry jokes!)

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You might be interested in a variety of hands-on ideas on how to introduce angles to your students. Check out

**Having Fun With Angles**. It explains how to construct different kinds of angles (acute, obtuse, right, straight) using items such as coffee filters, plastic plates, and your fingers. Each item or manipulative is inexpensive, easy to make, and simple for students to use. All of the activities are hands-on and work well for kinesthetic, logical, spatial, and/or visual learners.
## 7 comments:

Thanks so much for sharing this helpful information. Great title too.

I love this, Vicky! I didn't realize complementary angles did not need to be next to each other! I'm going to use these visuals for 90 and 180. Thanks!! I'm sure you must algebra so fun and understandable for your students!

I love tricks like this. I need to use them and I know there are many students out there who just need that extra something to get it to stick.

Very clever ideas to help students remember. You must be a great math teacher!

Very creative! The associations you show your students will certainly help them to remember which angle is which. I like the way you use different manipulatives to demonstrate angles.

Nice post and very informative! Thank you for sharing!

Love these ideas! Especially the one about complimentary angles! Thanks for bringing this one back!

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