What is sine
Let a right-angled triangle ABC with an acute angle α be given, then the sine of angle α will be the ratio of the opposite leg to the hypotenuse sin α = BC/AC
Also, to determine the sine of an angle, you can use a circle constructed in a Cartesian coordinate system, radius R and center at the origin O.
On the circle, mark the point P with coordinates (1; 0), now turn the ray OP by some angle α. Counterclockwise direction is considered positive, clockwise direction is negative.
The sine of the angle α will be the ratio of the ordinate of point YP to the radius of the circle.
sin α = YP/R, if the circle is unit (circle radius = 1), the formula will take the form sin α = YP .