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Explanation:
The angle -450 is not between 0 and 360. Add on 360 so that we do one full revolution to get -450+360 = -90.
The angle -90 isn't between 0 and 360 either. We repeat the last step by adding on 360 to get -90+360 = 270.
The result 270 is between 0 and 360, so we stop here.
The angle -450 and 270 both point in the same direction. Both point directly south. This is why they are considered coterminal angles.
