Math is more than just formulas. Understanding some mathematical principles about set theory is very useful to grasping complex concepts on type systems, as is understanding complexity a paramount to efficient data structure usages.

Graph theory is also extremely useful, as many programming problems can be modelled by a graph. I was very astonished, as I was developing a business application, to find out that the shortest path theorems were providing an elegant solution to a thorny problem that I had!