How to Find the Degrees in an Angle With Bisectors
A major focus of geometry is the study of angles. Angles are measured in degrees and can range from 0 to 360. A complete circle totals 360 degrees. Angle bisectors are line segments that cut the angle into two equal parts. Such line segments pass through an angle's vertex, or point where the original angle's sides meet. An angle may be measured by using a protractor, even if the angle has a bisector. The bisector simply needs to be ignored.
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Instructions
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Locate the angle you wish to measure.
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Find the vertex or the angle, or the point where the two lines meet.
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Position the center of protractor over the vertex of the angle. Make sure the baseline of the protractor lines up with the bottom line segment.
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Follow the opposite line segment until it reaches the inner scale, which is the bottom half-circle set of numbers. The number the line passes through is the measure of the angle in degrees. Make sure you are not following the line of the bisector.
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Check that you read your protractor correctly by comparing the angle to a 90-degree angle.
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Tips & Warnings
Be sure to keep your protractor lined up with the correct line segments.
If you measure one of the angles created by the bisector and multiple it by two, it should equal the measurement of the angle.
It is easy to confuse the bisector with a main line segment of the angle. Make sure you are using the correct segment and not the bisector. Measuring the bisector angle will give you a measurement that is only half of the angle's correct measurement.
