$cosx$, $sinx$ and $e^x$ go to a party. $sinx$ and $cosx$ are partying away but $e^x$ is miserable and anti social. $cosx$ and $sinx$ go up to $e^x$ and say ‘what’s wrong, why don’t you integrate?’

$e^x$ replied, It doesn’t make any difference does it?

This little joke should remind students about integrating the three terms. And a side note, they are really related, for instance in Complex Numbers.