Coterminal angles in the Cartesian plane have the same initial side and terminal side; the difference is that they can be obtained by adding or subtracting 360 degrees/2π radians, or multiples thereof. Check this site for further info:

Mathwords: Coterminal Angles

To do the problems above, just add 360 degrees/2π radians to the original angle, and subtract 360 degrees/2π radians from the original angle. For (a) this would be

and

.

What you add/subtract is arbitrary, since the directions didn't specify. I could have taken the original angle and added 720 degrees and 1080 degrees and those answers would also be valid. In other words, there are a whole lot of angles that are coterminal with each other.

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