Define the natural logarithm function in terms of the area under the curvey=1/x.

I need some help getting this one started. I also need to explain how to use this definition to find the derivative ofy= ln x,and explain how to use the derivative formula from above to prove that ln(a) + ln(b)= ln(ab)... I know it's a lot, but I could really use a push in the right direction. Thank you for the push...