(1-2²分之一﹚﹙1-3²分之一﹚﹙1-4²分之一﹚…﹙1-10²分之一﹚
=(1-1/2)(1+1/2)((1-1/3)(1+1/3)···(1-1/10)(1+1/10)
=1/2×3/2×2/3×4/3×3/4×5/3×···×9/10×11/10
=1/2×11/10
=11/20