Sine of an Angle
The sine of an angle is defined as being the side of a right triangle that is on the opposites side of that triangle from the indicated angle divided by the Hypotenuse of that Right Triangle.
Sine A = (Opposite side from A)/(Hypotenuse)
The Sine of an angle is never smaller than -1 and is never larger than +1.
The Sine of angel A is usually abbreviated as Sin A.