[Maxima] functions with diff and intergrate

[Hans W. Hofmann]

f(x):=(1-%e^(2*x))/(1+%e^(2*x));
df(x):=diff(f(x),x)$ 
df(1);
(%o11) Non-variable 2nd argument to diff:1
#0: df(x=1) -- an error.  To debug this try debugmode(true);

I'm not able to calculate diff'd and intergrate'd functions
how to do?

Gruß HW