Mathematics and Computer Education, April 1st, 2003
INTRODUCTION
The Law of Cosines is a fundamental theorem in trigonometry and relates the cosine of any angle in a triangle to its sides. In [Delta ]ABC, if we denote the lengths of its sides opposite to [angle ]A, [angle ]B, [angle ]C by a, b, c respectively, then the cosine law, applied to angle C, states that
c^sup 2^ = a^sup 2^ + b^sup 2^ - 2ab cosC
The history of this law could be traced back to Euclid's Elements, about 300 B.C.E. There one finds two geometric theorems, namely propositions 12 and 13 of Book II [3 ], which are equivalent to the Law of Cosines. We combine them here as
c^...
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