A very high gain margin or phase margin produces stable feedback systems, however they may be sluggish in operation. If the gain margin is close to unity of the phase margin is close to zero, the system will be highly oscillatory and produce overshoots with large amplitudes that take a while to settle.

Having a gain of 6 dB or phase margin of 30 - 35 degrees will give you a relatively stable system. However there exists cases where this may not be so.

:-)

First find the phase crossover frequency and then use that back into the magnitude of the transfer function.Then the gain margin is the reciprocal of that magnitude.

If you buy something for £1 and sell it for £3, then you've made 200% profit.

Edit

It is impossible to have 200% profit margin

It's also impossible to have a 100% profit margin

You can have a 200% MARKUP

But profit margin formula is 1 - (1 / (1 + (Markup))

So example

lets say you buy something for £1 and sell it for £3 then your markup 200% or £2

Your profit margin = 1-(1/1+(£2))

Profit margin = 67%

The top margin (and sides and bottom) is 1 inch.

1" is the default margin size.