evaluate the integral of lnx

this is an example of an integration by parts problem, we must use integration by parts to evaluate this integral;although this would not be entirely obvious as the integral does not seem to be the product of two functions. The key to successfully evaluating this integral is noting that lnx= 1*lnx we can consider this as a product of two functions now we can let u=lnx and differentiating both sides gives du=1/x dx. we also let dv=1 dx and hence integrating both sides yields v=x. applying the integration by parts formula will give us the integral of lnx being equal to xlnx -x + C