When I calculate an integral of the form:
Integrate[1/((f(a)+I*x)*(f(b)+I*x)),{x,-Infinity, Infinity}],
where I is the imaginary unit. How can I assume that f(a)
is a positive function for all values of its argument? I am not
interested in changing the function to a constant and then
assuming the constants are >0 since the real problem is
complicated and I need to keep f(a) a function.
