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Patterns + Functions


 

 

 


What is a protractor?

A protractor is a clear plastic device to measure angles from 0 to 180 degrees.  You can use a protractor to measure an angle in degrees. 

 

How do I measure angles using a protractor?  There are two sets of numbers, so you can measure angles from either side of the protractor. 

To decide which scale to use, look at the angle you're measuring. If it is greater than a right angle (more than ninety degrees) then use the scale that has numbers greater than 90. If the angle is acute (measures less than 90 degrees), use the scale which has numbers less than 90.

Example: right angle

A right angle measures 90 degrees. Measure an angle by measuring the distance between its sides.

 

 

Place the protractor on the angle so that the center point is on the vertex and the zero line is along one side of the angle. Follow the scale beginning at zero and read the measure of the angle where the other side of the angle intersects the scale on the protractor.

 

Example: acute angle

An acute angle is less than 90 degrees.

 

 

Example: obtuse angle

An obtuse angle is greater than 90 degrees.

 

 

Remember:
A protractor is a clear plastic device to measure angles from 0 to 180 degrees. You can measure angles from either side of the protractor.

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