sin(n+1) = sin(n) + (1/m)cos(n) and
cos(n+1) = cos(n) – (1/m)sin(n+1)
where m is the value supplied by the user.
The word SIN uses the top three numbers on the stack to calculate the next members of the series, replacing the top of the stack with the next sine and the second to top with the next cosine. This gives the equation SIN(m,cos(n), sin(n) –m, cos(n+1),sin(n +1)).
If m is a large value, the starting value should be correspondingly high; and the higher the starting value, the more accurate the sine-wave.