Is it possible for N to be negative?

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Is it possible that N < 0? and |N| > P?

Yes, counter-clockwise encirclements give N < 0 since N is the number of clock-wise encirclements. For example, if you have two counter-clockwise encirclements of the -1 point then N = -2.

If N is not equal to -P then the closed loop system will be unstable.

--Mary Dunlop 15:58, 6 November 2006 (PST)