由题可知x^2>1 x>1或x<-1
令x=secα,α∈[0,π/2]∪[-π,-π/2]
tanα>0
∫dx/√(x^2-1)=∫dsecα/|tanα|
=∫dsecα/tanα=∫secαtanαdα/tanα=∫secαdα
=ln|secα+tanα|+C=ln|x+√(x^2-1)|+C
所以∫dx/√(x^2-1)=ln|x+√(x^2-1)|+C
∫dx/√(x^2-1)
let
x=secu
dx=secu.tanu du
∫dx/√(x^2-1)
=∫secu.tanu du/ tanu
=∫secu du
=ln|secu + tanu| + C
=ln|x + √(x^2-1) | + C