Trigonometry is the branch of science that studies triangles, paying particularly close attention to the measurements between the triangle's points and the angles of the triangle's three corners. Trigonometry is used for a variety of fields, including tailoring, landscaping and architecture. One great reason for people studying trigonometry to have charts is that there are many different formulas used to determine angles and measurements. Having a chart that showed different kinds of triangles and the formulas associated with them is quite handy!