Question

Would I be right if I said 21pi/10 and -pi/10 are two angles coterminal with pi/10?

Answer 1

A co-terminal angle is found by subtracting (or adding) 2 pi to the angle.
and co-terminal angles are always positive.

Answer 2

sorry, co-terminal angles can be negative.
and you are correct.

Answer 3

okay thanks! :)

Answer 4

yes co-terminal means the magnitude of the angle away from horizontal axis

Answer 5

but the 2nd co-terminal angle will be pi/10 - 2pi = -19 pi/10 and not -pi/10