令x=asint原式=1/[(a^2cost^2)^5/2]dsint=1/(a^5cost^4)dt=(sint^2+cost^2)/(a^5cost^4)dt=sint^2/(a^5cost^4)dt+1/(a^5cost^2)dt=tant^2/a^5dtant+1/a^5dtant=tant^3/3a^5+tant/a^5+C最后再将t=arcsin x/a 代回即可...