设f(x)=arctanx+arctanx^-1f'(x)=1/(1+x^2)+1/(1+(x^-1)^2)*(-x^-2)=0故f(x)恒等于常数C带入x=1得f(1)=π/2把原式-1到1分成-1到0和0到1再把arctane^x分成arctane^x和arctane^-x
