"sin" is used in calculators to measure the sine of an angle. There are 2 ways to calculate sin(x).
First, draw a right triangle with one angle with measure x. The hypotenuse of the right triangle should be 1. If x is more than a right angle, continue the leg and hypotenuse of the right triangle. Out of the 4 angles that are formed (2 pairs), select the smallest pair, and replace x with that. The length of the opposite leg relative to angle x is the sine of the angle. (Easiest when angle is given in degrees)
Draw a circle with radius one. Then, starting from the top, travel x around the circle. The y-value of the location is the sine of the angle. (Easiest when angle is given in radians)