An introduction to mathematics, by A. N. Whitehead.

COORDINATE GEOMETRY 123
to this is a straight line, and conversely to
every straight line there corresponds an equation of this form. It is fortunate that the
simplest among the geometrical loci should
correspond to the simplest among the algebraic forms. Indeed, it is this general
correspondence of geometriçal and algebraic
simplicity which gives to the whole subject
its power. It springs from the fact that the
connection between geometry and algebra is
not casual and artificial, but deep-seated and
essential. The equation which corresponds
to a locus is called the equation of (or "to")
the locus. Some examples of equations of
straight lines will illustrate the subject.
L Y' \ -
Fig. 14.