The sine of the complement of an arc or angle. See Illust. of Functions.
- In a right triangle, the ratio of the length of the side adjacent to an acute angle to the length of the hypotenuse.
- The abscissa at the endpoint of an arc of a unit circle centered at the origin of a Cartesian coordinate system, the arc being of length x and measured counterclockwise from the point (1, 0) if x is positive or clockwise if x is negative.