This is an html5 applet to explore the properties of the graphs of cosine functions. The parameters $a$, $b$, $c$ and $d$ included in the definition of a cosine function of the form
$f(x)= a \: cos{(b x+c)}+d$
may be changed and therefore the graph of function $f$ explored. A radio button may be used to graph cos(x) in order to compare and therefore better understand the properties of $a \: cos{(b x+c)}+d$.