trigonometric Function (also called a circle Function) is an angular Function; They are important in studying trigonometric and modeling periodic phenomena and many other applications. trigonometric Function usually defines as contain the ratio between the two sides of this Angle right Angle trigonometric function can equally define as the length of various lines on the unit circle. More modern definitions express them as infinite numbers or specific differential Equation solutions, allowing them to extend to arbitrarily positive and negative number values, and even complex number values.