f(x) walks into a bar and the barman says "We don't cater for functions." sin(x), cos(x) and exp(x) were at a party, and while sin and cos were having a great

f(x) walks into a bar and the barman says "We don't cater for functions." sin(x), cos(x) and exp(x) were at a party, and while sin and cos were having a great time, exp 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."