NProduct
NProduct[f, i, imin, imax] gives a numerical approximation to the product . NProduct[f, i, imin, imax, di] uses a step di in the product.
See notes for NSum. See The Mathematica Book on the web: Section 1.6.2, Section 3.9.1 and Section 3.9.4.
Further Examples
NProduct[f, 
i, imin, imax
] gives a numerical approximation to the product 
. 
i, imin, imax, di
] uses a step di in the product. 