Measurements: Distance and length
• A metric is a rule for the determination of distance
between points in a space.
• The simplest is the rule for determining the
shortest distance between two points in a flat
plane, called the Pythagorean or straight-line
metric.
• Pythagoras’s theorem tells us that the square of
this length is equal to the sum of the squares of the
lengths of the other two sides. So a simple formula
results: