Like distances and directions on a map, there must be some common frame of reference for angle
figures to have any meaning. In this case, directly right is considered to be 0
o
, and angles are counted
in a positive direction going counter-clockwise: (Figure 2.2)
The idea of representing a number in graphical form is nothing new. We all learned this in grade
school with the “number line:” (Figure 2.3)
We even learned how addition and subtraction works by seeing how lengths (magnitudes) stacked
up to give a final answer: (Figure 2.4)
Later, we learned that there were ways to designate the values between the whole numbers marked
on the line. These were fractional or decimal quantities: (Figure 2.5)
Later yet we learned that the number line could extend to the left of zero as well: (Figure 2.6)
These fields of numbers (whole, integer, rational, irrational, real, etc.) learned in grade school
share a common trait: they’re all one-dimensional. The straightness of the number line illustrates
this graphically. You can move up or down the number line, but all “motion” along that line is
restricted to a single axis (horizontal). One-dimensional, scalar numbers are perfectly adequate
for counting beads, representing weight, or measuring DC battery voltage, but they fall short of