# Help with integral of Log

1. Jan 10, 2009

### atwong713

1. The problem statement, all variables and given/known data

$$\int$$$$\int-xlogy dy dx$$

the only problem i have is finding the integral of logy
i know i have to integrate my parts with u = logy and dv=dy
the book says the the integral of logy is ylogy-y but isn't the derivative of logy equal to 1/ylna where a is the base?
so isn't the integral of logy equal to ylogy-y/ln10 because of the base 10?
can someone clarify this for me?

2. Jan 10, 2009

### jgens

I know some calculus books (especially the older ones I have looked at) use log(y) to designate the natural logarithm. Are you certain this isn't the case?

3. Jan 10, 2009

### atwong713

oooo it is thanks makes a lot more sense now