Question

要好,不要复制.易懂.计算(1-1/2²)(1-1/3²)(1-1/4²).(1-1/10²)

Answer 1

(1-1/2²)(1-1/3²)(1-1/4²).(1-1/10²)

=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4).(1-1/10)(1+1/10)

=1/2×3/2×2/3×4/3×3/4×5/4.×9/10×11/10

=1/2×11/10

=11/20