(1-1/2�0�5)(1-1/3�0�5)...(1-1/n�0�5)=(1+1/2)(1-1/2)(1+1/3)(1-1/3)...(1+1/n)(1-1/n)=[(1+1/2)(1+1/3)...(1+1/n)] * [(1-1/2)(1-1/3)...(1-1/n)]=[(3/2)(4/3)...(n+1)/n] * [(1/2)(2/3)...(n-1)/n]=(n+1)/2 * (1/n)=(n+1)/(2n)所以 n 趋于正无穷时,极限是 1/2.
1-1/2^2=(1+1/2)*(1-1/2)=1/2*3/21-1/3^2=(1+1/3)*(1-1/3)=4/3*2/31-1/4^2=(1+1/4)*(1-1/4)=5/4*3/4。。。1-1/n^2=(1+1/n)*(1-1/n)=(n+1)/n *(n-1)/n通过相乘1/2*3/2*4/3*2/3。。。*(n+1)/n *(n-1)/n=(n+1)/2n所以其极限为1/2