Problem A: The global positioning system GPS uses the fact that a receiver can get the
difference of distances to two satellites (each GPS satellite sends periodically signals
which are triggered by an atomic clock. While the distance to each satellite is not
known, the difference from the distances to two satellites can be determined from the
time delay of the two signals. The receiver does not need an atomic clock).
Given two satellites P=(2,0,0), Q=(0,0,0) in space. Identify the quadric,
whose distance to P is by 1 larger than the distance to Q. How many GPS
satellites does your GPS receiver have to 'see' in space so that it
can determine the position?
