If and be the th roots of unity which subtend right angle at the origin. Then must be of the form
Explanation for the correct option.
Find the representation of .
It is given that and are the th roots of unity. So, .
Also, and subtend right angle at origin. So, . Thus,
Thus, but because .
Thus, . This is true only when is of the form .
So, must be of the form .
Hence, the correct option is D.