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Geometry Course
Measuring Angles - Part 4
Free Geometry Basics Course
Part 1
Terms in Geometry
Part 2
Types of Angles
Part 3
Part 4
Measuring Angles
Part 5
Bisectors, Congruencies, Theorems
Part 6
Geometry Help
Mathematicians Review
Conic Sections
Pythagorean Theorem
Related Resources
Measurement Formulas
Recommended Resources
Area Calculator
Introduction to Polygons

The size of an angle will depend on the opening between the two sides of the angle (Pac Mac's mouth) and is measured in units that are referred to as degrees which is indicated by the ° symbol. To help you remember approximate sizes of angles, you will want to remember that a circle, once around measures 360°. To assist you to remember approximations of angles, it will be helpful to remember the following:

Think of a whole pie as 360°, if you eat a quarter (1/4) of it the measure would be 90°. If you ate 1/2 of the pie? Well, as stated above, 180° is half, or you can add 90° and 90° - the two pieces you ate!

If you cut the whole pie into 8 equal pieces. What angle would one piece of the pie make? To answer this question, you can divide 360° by 8 (the total by the number of pieces). This will tell you that each piece of pie has a measure of 45°.

Usually, when measuring an angle, you will use a protractor, each unit of measure on a protractor is a degree °.
Note: The size of the angle is not dependent on the lengths of the sides of the angle.

In the above example, the protractor is used to show you that the measure of angle ABC is 60°

Try a few best guesses, the angles below are approximately 10°, 50° , 150°,


1. = approximately 150°

2. = approximately 50°

3 = approximately 10°

Part 5: Bisectors, Congruencies and Theorems

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