Yeh, I used to think that about a lotta mathsy stuff, but it really is useful.. Im doing a masters in maths, operational research, statistics and economics at the moment and its SO useful in economics and operational research.. in economics if you can make a mathematical model an economy, basically by differentiating you can maximise or minimise things, which means in real life you'd have a good estimate of how to get an optimal economy in operational research (which is basically just modelling business' problems mathematically, it just sounds flash), you can do the same integration is also helpful for stuff like finding the area under the graph, which might for example symbolise profits or something, which you might want to maximise too