In DSP, the exact value of a mathematical function usually isn’t needed: a degree of inaccuracy usually can be tolerated, and computational speed usually is a primary concern. The right combination of accuracy and speed is very much application-specific.
Approximation of mathematical functions, therefore, is an important subject in DSP. Highly accurate approximations are well known. However, here we present some less-well known approximation DSP tricks which provide an outstanding combination of speed and accuracy.