(1+1/2²)*(1-1/3²)*(1-1/4²)*……(1-1/9²)*(1-1/10²) 急 90°

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(1+1/2²)*(1-1/3²)*(1-1/4²)*……(1-1/9²)*(1-1/10²) 急 90°
(1+1/2²)*(1-1/3²)*(1-1/4²)*……(1-1/9²)*(1-1/10²) 急 90°

(1+1/2²)*(1-1/3²)*(1-1/4²)*……(1-1/9²)*(1-1/10²) 急 90°
第一个括号是减号吧!(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*……9/10*11/10=1/2*11/10=11/20

=(5/4)*(1+1/3)*(1-1/3)*(1+1/4)*(1-1/4)*……(1+1/9)*(1-1/9)*(1+1/10)*(1-1/10)
=(5/4))*(1+1/3)*(1+1/4)*(1+1/5)*……(1+1/10)*(1-1/3)*(1-1/4)*……(1-1/10)
=11/12