N趋近于无穷大,{tan(π/4+2/n)}n次方的极限为e^4
[tan(π/4+2/n)]^n={[1+tan(2/n)]/[1-tan(2/n)]}^n={1+[2tan(2/n)]/[1-tan(2/n)]}^n
={1+[2tan(2/n)]/[1-tan(2/n)]}^{{[1-tan(2/n)]/[2tan(2/n)]}*2ntan(2/n)/[1-tan(2/n)]}
下面是极限过程：
=e^{2ntan(2/n)/[1-tan(2/n)]}=e^[2*n*(2/n)/(1-0)]=e^4