find a positive and a negative coterminal?

45 + 360 = 405 degrees is a positive coterminal angle

45 - 360 = -315 degrees is a negative coterminal angle

13pi/6 + 2pi = 13pi/6 + 12pi/6 = 25pi/6 is a positive coterminal angle.

13pi/6 - 4pi = 13pi/6 - 24pi/6 = -11pi/6 is a negative coterminal angle.

If the angle is in degrees, adding or subtracting a multiple of 360 gives you a coterminal angle. If the angle is in radians, adding or subtracting a multiple of 2pi gives you a coterminal angle.

Conterminal