f(x) walks into a bar and the barman says "We don't cater for functions."<p><i>sin(x)</i>, <i>cos(x)</i> and <i>exp(x)</i> were at a party, and while <i>sin</i> and <i>cos</i> were having a great time, <i>exp</i> was sitting by himself.  When asked why he wasn't joining in he said "Everytime I try to integrate I just end up with myself."