This is a formula sheet for "Introduction to Trigonometry", and contains all equations and properties of trigonometric functions encountered in a first course on this subject. Topics covered include definitions of trig functions, their domains and ranges, trig identities, parity formulas, angle sum/difference formulas, double and half-angle formulas, the laws of sine and cosine, triangle area formulas, graphs of all trigonometric functions and their inverse functions, a table of values for speci