Sure. For example in trigonometry, there are a handful of identities that are worth memorizing, but most of them you just look them up and use them. What if you had a list of these somewhere in handy form -- MathType equations in a Word document, for example. It would be easy to share them with others studying the same subject, and they could share with you formulas they had collected. And since they're in a re-usable format, they'd be easy to use in homework, presentations, or otherwise.