I understood coterminal angles as angles that have the same terminal angle value. By this logic, why aren't 135 and 315 coterminal? They both have a terminal angle of 45.
Is my interpretation of coterminal angles wrong?
Two angles a are coterminal if their difference is a multiple of 360°. What that means is that two angles are coterminal when they start and end in the same place. Examples of Coterminal angles are
Another way of explaining is that Coterminal angles are angles in standard position (angles with the initial side on the positive x-axis) that have a common terminal side. For example 30°, –330° and 390° are all coterminal.(look below).Here –330° is the negative coterminal angle of 30° and 390°is positive coterminal angle of 30°.
So according to your question 135 and 315 cannot be coterminal as they do not lie on one another.hope that helps