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

190 INTRODUCTION TO MATHEMATICS
through the point on OX marked -, instead
of drawing it in its actual position on the
figure.
It is easy to construct a 'sine' function in
Fig. 28.
which the period has any assigned value a.
For we have only to write. 7rx
y=sin-,
and then. 7r(x+a). f7 9rx. 2vrx
sin =sin +7r =sin
a a a
Thus the period of this new function is now a.
Let us now give a general definition of what