Two [[angle|angles]] are **coterminal** (ending the same) if the final result of their rotation is equivalent. Coterminal angles are *not necessarily congruent*, since *the number of revolutions* and the *direction of rotation* could be different Two angles $\alpha$ and $\beta$ are coterminal if and only if they differ by an integer number of revolutions. In radians:$\frac{\alpha-\beta}{2\pi}\in\mathbb{Z}$ In degrees: $\frac{\alpha\degree-\beta\degree}{360\degree}\in\mathbb{Z}$