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.
