# Question Video: Identifying a Right Angle from Its Measure Mathematics

Which of the following is a right angle? [A] Option A [B] Option B [C] Option C [D] Option D [E] Option E

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### Video Transcript

Which of the following is a right angle? Options (A), (B), (C), (D), and (E).

In this question, we are asked to identify which of five given angles is a right angle. We can do this by recalling that a right angle is an angle whose measure is 90 degrees, that is, a quarter of a full turn. All five of the angles have given measure, and we can see that only the angle in option (C) has a measure of 90 degrees, so it is the only right angle.

We could stop here. However, we can also classify the types of each of the other four angles using their measures. First, we recall that an angle with measure between 180 degrees and 360 degrees is a reflex angle. So, the angle in option (A) is a reflex angle. Second, we recall that an angle with measure between zero degrees and 90 degrees is an acute angle. So, the angle in option (B) is acute.

Third, we recall that an angle with measure between 90 degrees and 180 degrees is an obtuse angle. So, the angle in option (D) is obtuse. Finally, we can recall that an angle with measure 180 degrees is called a straight angle. So, option (E) is a straight angle. And we can conclude that only the angle in option (C) is a right angle.