Hello everyone, this one might seem easy to you but it's driving me insane. Q) Suppose f(x)=int(1/t.dt) where the upper limit=x, lower limit=1 ; for x>0. Without evaluating the integral show that for any x,y>0, f(x)+f(y)=f(xy). where you may consider a substitution s=xt in the left-hand side. Thanks for your help in advance.