求不定积分∫1/(x^4*√(1+x^2))dx

Question

求不定积分∫1/(x^4*√(1+x^2))dx

Answer 1

x=tant,dx=(sect)^2dt
原积分=S1/((tant)^4*sect)*(sec)^2dt
=Scost^3/sint^4 dt
=S(1-sint^2)/sint^4d(sint)
=S(1/sint^4)dsint-1/sint^2)dsint
=-1/3*（sint）^（-3）+1/sint+c
=-1/3*(x/√(x^2+1))^(-3)+√(x^2+1) /x +c