CORDIC: How Hand Calculators Calculate

of two books and several research articles, and is currently heavily involved in the math education of prospective high school math teachers. He enjoys singing bass in the Oratorio Society of Queens, and loves to see how the math we teach can be applied. Almost every calculus teacher I ask answers the question, “How do calculators com-pute sines and cosines? ” with the words, “Taylor Polynomials. ” It comes as quite a surprise to most that, though it is reasonable to use Taylor polynomials, it is really a method known as CORDIC that is used to compute these and other special func-tions. CORDIC was discovered by Jack Volder in 1959 while working for the Convair corporation and was developed to replace the analog resolver in the B-58 bomber’s navigation computer. What was needed was a program that could compute trigono-metric functions in real time without the use of much hardware. CORDIC, an acronym for COordinate Rotation DIgital Computer, was the solution. CORDIC is fast; much faster than Taylor series for the low level hardware used on a calculator, though whe