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Teach the degree system, the use of a protractor to measure angles, and how to construct them.
Introduction to degrees and angle measures.
How do we assign a precise number to a turn? Ancient mathematicians divided a full circular turn into 360 equal parts. Each tiny part is called 1 degree, written as .
To make measuring easier, we use certain benchmarks based on parts of a circle:
How to read and use a protractor.
The standard tool for measuring angles is a protractor. It looks like a half-circle that is divided into 180 equal units, each representing 1 degree.
Notice that the protractor has two sets of numbers on its curved edge: an inner scale and an outer scale. Why two? Because it allows you to easily measure angles opening from the left or the right without having to flip the tool upside down!
Visual of a protractor correctly aligned on an angle.
Clean scientific diagram of a protractor correctly placed over an acute 50 degree angle. The center point of the protrac…
Identify common protractor errors.
A student measures a sharp, acute angle with a protractor but reads the measurement as . What most likely went wrong?
Steps to construct an angle and defining angle bisector.
Creating an angle is just as easy as measuring one. Let's draw a angle:
Order the steps to draw an angle.
Arrange the steps in the correct order to successfully draw a 60° angle.