Two angles are said to be coterminal if they locate the same point on the circumference.
This means that two angles are coterminal if they differ by a multiple of 360°: if you make a certain numbers of whole turns, in either direction, you end up in the same point.
So, you solve problems like this by adding or subtracting 360, until you are inside the interval [0,360].
In this case, you only need to add 360 once:
[tex] -315+360=45 [/tex]
So, -315° and 45° are two coterminal angles.
