GEOMETRIC METHOD

Geometric Method

A Geometric Method of Finding the Trigonometric Ratios of 22 ½º and 75 º

Geometric Methods of finding trigonometric ratios of some special angles have always interested mathematics educators and pupils alike. Geometric methods of finding trigonometric ratios of some special angles like sin (18°) and cos (36°) can be found in S.L. Loney's Trigonometry (Volume I).

In this article, we give a geometric method of finding all the trigonometric ratios of 22 ½º and 75º. It is to be noted we can derive the ratios by using the half angle formula and sum of angles formula. However, the interest is ...