Trigonometry is the study of the geometry of triangles. Here you investigate the relationship of the sides and angles of triangles using the functions of sine, cosine and tangent. The study of trigonometry goes way back and was used to navigation on the oceans of the world. Captains needed to understand trigonometry in much detail. The captain of a vessel was able determine the location of the ship by using the stars and realizing their positions varied each and every day throughout the year using trigonometry.