Sine
![](/Images/godic/202501/16/Webysther_20160305_-_Ciclo_trigonométrico.svg3714.png")
![](/Images/godic/202501/16/Trigono_sine_en2.svg3714.png")
![Illustration of a unit circle. The radius has a length of 1. The variable t is an angle measure.](/Images/godic/202501/16/Unit_circle.svg3715.png")
![](/Images/godic/202501/16/Circle_cos_sin3715.gif")
Sine, in mathematics, is a trigonometric function of an angle. The sine of an angle is defined in the context of a right triangle: for the specified angle, it is the ratio of the length of the side that is opposite that angle (that is not the hypotenuse) to the length of the longest side of the triangle (i.e., the hypotenuse).