The Magic Calculator and The Sine Addition Formula
Bryan Dorner
Mathematics Department
Pacific Lutheran University
Tacoma, WA 98447
Phone: (253) 535-8737
E-mail: dornerbc@plu.edu
ABSTRACT
This paper describes how beginning trigonometry students can compute the sine and cosine
of any angle to any degree of accuracy using only simple geometry and a calculator with
a square root key. The ideas in this algorithm also provide a simple derivation of the
angle addition identity: sin(x+h)=sin(x)cos(h)+cos(x)sin(h).
