Blackman-Nuttall 4-term cosine-sum window on [-1/2 1/2] (exact rationals for exact input)
BlackmanNuttallWindow[x]
Plot[BlackmanNuttallWindow[x], {x, -1, 1}]
→ -Graphics-Plot3D[BlackmanNuttallWindow[x]BlackmanNuttallWindow[y], {x, -1, 1}, {y, -1, 1}, PlotRange -> All]
→ -Graphics3D-BlackmanNuttallWindow[0.1]
→ 0.7982580969501283