(1+e^x)/(1+e^(-x))
= e^x * (1+e^x)/【e^x * (1+e^(-x))】(即分子分母各乘e^x)
= e^x * (1+e^x)/(e^x+1)
= e^x (分子分母约分,约去(1+e^x))
∴ ln【(1+e^x)/(1+e^(-x))】
= ln (e^x)
= x
(1+e^x)/(1+e^(-x))
= e^x * (1+e^x)/【e^x * (1+e^(-x))】(即分子分母各乘e^x)
= e^x * (1+e^x)/(e^x+1)
= e^x (分子分母约分,约去(1+e^x))
∴ ln【(1+e^x)/(1+e^(-x))】
= ln (e^x)
= x