(1-1/2^2)(1-1/3^2)……(1-1/2002^2)
=(1+1/2)(1-1/2)(1+1/3)(1-1/3)……(1+1/2002)(1-1/2002)
=3/2×4/3×……×2003/2002×1/2×2/3×……×2001/2002
=2003/2×1/2002
=2003/4004
(1-1/2^2)(1-1/3^2)……(1-1/2002^2)
=(1+1/2)(1-1/2)(1+1/3)(1-1/3)……(1+1/2002)(1-1/2002)
=3/2×4/3×……×2003/2002×1/2×2/3×……×2001/2002
=2003/2×1/2002
=2003/4004