Video Transcript
Which of the following is the
definition of a zero angle? Option (A) it is an angle whose
measure is zero degrees, as its sides coincide. Option (B) it’s an angle whose
measure is 90 degrees, as its sides are perpendicular to each other. Or is it option (C) it is an angle
whose measure is 180 degrees, as its sides are in opposite directions?
To answer this question, we can
start by recalling that a zero angle is any angle with a measure of zero
degrees. This is enough information to
eliminate options (B) and (C) and conclude that the answer is option (A). However, we can also answer this
without the options using the definition of an angle and an angle’s measure.
We can recall that an angle is two
rays that share a starting point and the rotation required to rotate one side onto
the other side, such as angle 𝐴𝐵𝐶 as shown. We can then recall that a full
rotation is defined to have a measure of 360 degrees. This means that an angle of measure
180 degrees will have its sides opposite each other. This is called a straight
angle. An angle of measure 90 degrees
means it takes a quarter turn to rotate one side onto the other. This is called a right angle. And it is also used in the
definition of saying that two sides are perpendicular. Finally, if an angle has measure
zero degrees, then it takes no rotation to rotate one side onto another. This means that its sides must
coincide.
Hence, the answer is option
(A).
