# Formulas to Help You in Trigonometry

Many of the formulas used in trigonometry are also found in algebra and analytic geometry. But trigonometry also has some special formulas usually found just in those discussions. A formula provides you a rule or equation that you can count on to work, every single time. A formula gives a relationship between particular quantities and units. The main trick to using formulas is to know what the different letters represent. In the formulas given here, you have: *r* (radius); *d* (diameter or distance); *b* (base or measure of a side); *h* (height); *a*, *b*, *c* (measures of sides); *x*, *y* (coordinates on a graph); *m* (slope); *M* (midpoint); *h*, *k* (horizontal and vertical distances from the center); *θ* (angle theta); and *s* (arc length). The formulas particular to trigonometry have: sin (sine), cos (cosine), and tan (tangent), although only *sin* is represented here.