2. ∫dx/(x√(x^(2)–1)).
[m]\frac{1}{x}=t[/m]
[m]x=\frac{1}{t}[/m]
[m]dx=-\frac{dt}{t^2}[/m]
[m]\sqrt{x^2-1}=\sqrt{\frac{1}{t^2}-1}=\frac{\sqrt{1-t^2}}{t}[/m]
[m]\int \frac{dx}{x\sqrt{x^2-1}}=-\int \frac{dt}{\sqrt{1-t^2}}=-arcsint+C=[/m]
[m]=-arcsin\frac{1}{x}+C[/m]