Sine of an angle

in a circle whose radius is unity, the sine of the arc that measures the angle; in a right-angled triangle, the side opposite the given angle divided by the hypotenuse. See Trigonometrical function, under Function.

See also: Sine

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
We now know that the sine of an angle is well defined.
(When the altitude is outside of the triangle, one will need to use the fact that sin (180[degrees] - A) = sin A to prove the result, and this easily follows from the definition of the sine of an angle.) If we draw an altitude to side AB and proceed similarly, we obtain