Answer:
Option 1 and 3 - It is on the y-axis and It is a multiple of 90˚.
Step-by-step explanation:
To find : Why is 270° a quadrantal angle?
Solution :
Quadrantal Angle is defined as
One that is in the standard position and has a measure that is a multiple of 90° (or
radians).
A quadrantal angle will have terminal side on the x-axis or y-axis.
i.e. the angles 0°, 90°, 180°, 270°, 360°, 450°, ... as well as –90°, –180°, –270°, –360°, ...
By definition,
270° is a Quadrantal angle as it is on y-axis and it is a multiple of 90°.
Therefore, option 1 and 3 is correct.