[tex]\int {\frac{1}{x} lnx} \, dx = \int {\ (lnx)' lnx} \, dx = ln^2x - \int {\frac{1}{x} lnx} \, dx[/tex]
Adaugam integrala din 1/x lnx dx in dreapta si in stanga :
[tex]2\int {\frac{1}{x} lnx} \, dx = ln^2x\\\\\int {\frac{1}{x} lnx} \, dx = \frac{ln^2x}{2}[/tex]
