When reading an obtuse angle, especially when using a protractor that provides two possible measurements, you must choose the larger reading because an obtuse angle is defined as being greater than 90 degrees.
Understanding Obtuse Angles
An obtuse angle is an angle that measures more than 90 degrees but less than 180 degrees. When you use a protractor to measure an angle, you might notice two scales, one starting from 0 on the left and increasing clockwise, and the other starting from 0 on the right and increasing counter-clockwise.
Reading Obtuse Angles with a Protractor
The key to correctly reading an obtuse angle with a protractor lies in identifying which scale to use or, if both readings are presented, knowing which one represents the obtuse measure.
Based on the provided reference:
- When measuring an angle with a protractor, you might be presented with two possible degree measurements.
- For example, the reference mentions having choices like 20 degrees or 160 degrees.
- Since an obtuse angle is bigger than 90 degrees, you must select the measurement that is greater than 90.
- In the example from the reference (20 degrees vs. 160 degrees), you have to choose 160 degrees because 160 is greater than 90, whereas 20 degrees is an acute angle.
So, to read an obtuse angle accurately with a protractor, align the protractor correctly and then:
- Identify which scale starts at 0 along one side of your angle. Read the measure where the other side of the angle crosses that scale.
- Alternatively, if you see both possible readings (as described in the reference), identify the measurement that is larger than 90 degrees. This is the correct reading for the obtuse angle.
In summary, when faced with multiple readings on a protractor for an angle that is clearly obtuse (looks wide, greater than a right angle), always select the value that is above 90 degrees.
