Trigonometric Functions

Trigonometric functions relate an angle of a right triangle to the ratios of two of its side lengths, and are used throughout navigation, mechanics and astronomy. The six standard functions are sine, cosine, tangent and their reciprocals cosecant, secant and cotangent, with sine, cosine and tangent the most commonly used; each also has an inverse and a hyperbolic counterpart. They were originally defined only for acute angles using right triangle geometry, but modern mathematics extends them to all real and complex numbers through the unit circle and analytic methods. This extension lets them describe periodic, cyclical phenomena and underlies techniques such as Fourier analysis, making them some of the most widely used functions in mathematics and the applied sciences. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/