Mentally compute cosine

Ronald Doerfler presents a simple approximation for the cosine of an angle in degrees in his book Dead Reckoning. cos d° ≈ 1 – d(d + 1)/7000 The approximation is good to about three digits for angles between 0° and 40°. Although cosine is an even function, the approximation above is not, and the error […] The post Mentally compute cosine first appeared on John D. Cook....

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