Result is sin(Number)
which should be preferred for portability.
In coroutining mode, if Number is uninstantiated, the call to sin/2 is delayed until this variable is instantiated.
Success:
sin(1.5708, 1.0).
sin(-1.5708, Result). (gives Result = -1.0)
sin(0, Result). (gives Result = 0.0)
Fail:
sin(1, 0.0).
sin(6, 3).
sin(5, r).
Error:
sin(A, 6.0). (Error 4).
sin(4 + 2, -0.279415). (Error 24).