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In this lesson, you will learn how to name an angle and how to measure an angle in degrees. In order to name an angle, the vertex of the angle must be the center letter. We can then, for example, name angle ABC as exactly the same as angle CBA because the vertex B in this example is in the center in both names. Both names for the angle are equally valid. In order to measure the angle, we use a protractor. We put the vertex of the angle in the center of the protractor and use the numbers on the edge of the protractor to measure how far open or closed the two rays that make up the angle are.