n Learning and Teaching Mathematics - An alternative trig formula for solving triangles

Abstract

This article presents an interesting trigonometry formula that can be used when solving triangles given two sides and an included angle. When the known dimensions are in SAS configuration one generally uses the cosine rule to first work out the length of the side opposite the given angle. This is then followed by a second step in which the sine rule is used to determine the size of the desired angle. The alternative formula presented here allows one to determine the size of the desired angle in one easy step. The formula is presented below in terms of angle B, the desired angle.