The sine wave is the fundamental wave shape for several
reasons. It has harmonious mathematical properties – it is
the same sine shape you may have studied in high school
trigonometry class. The voltage in your wall outlet varies as
a sine wave. Test signals produced by the oscillator circuit
of a signal generator are often sine waves. Most AC power
sources produce sine waves. (AC signifies alternating current,
although the voltage alternates too. DC stands for direct
current, which means a steady current and voltage, such
as a battery produces.)