Using the integral definition 
Possible Duplicate:
Natural Logarithm and Integral Properties 

I was asked to prove that ln(xy) = ln x + ln y  using the integral definition.
While I'm not asking for any answers on the proof, I was wondering how to interpret and set-up this proof using the "integral definition" (As I am unsure what that means.)
EDIT
And to prove that ln(x/y) = ln x - ln y
Is it right to say this?
$$\ln(\frac{x}{y})=\int_1^{\frac{x}{y}} \frac{dt}{t}=\int_1^x \frac{dt}{t}-\int_x^{\frac{x}{y}}\frac{dt}{t}.$$

By definition,
$$\ln w=\int_1^w \frac{dt}{t}.$$
Thus
$$\ln(xy)=\int_1^{xy} \frac{dt}{t}=\int_1^x \frac{dt}{t}+\int_x^{xy}\frac{dt}{t}.$$
Now make an appropriate change of variable to conclude that the last  integral on the right is equal to $\ln y$.
