How to do matrix and vector math in Objective-C?

I did not see it mentioned but GLKit provides vector / matrix functions for math types commonly used in computer graphics.

Since iOS 4.0, the SDK includes Apple's Accelerate framework, which contains a number of C matrix and vector functions that are especially optimized to run on iOS hardware.

The function names and documentation is kind of cryptic, but if performance is particularly important, it might be your best choice.