The basic formulas of trigonometry are the formulas that establish the relationships between the main trigonometric functions. Trigonometry formulas (trigonometric formulas) or trigonometric identities describe the relationships between sine, cosine, tangent and cotangent and are used to solve mathematical problems. The appendix contains the basic trigonometric formulas, and for convenience are grouped by their purpose. Using these formulas, you can solve almost any problem from the standard course of trigonometry.