... cos 3xdx = −1 3 x2cos 3x +2 3 I1.Ta cˆa`n t´ınh I1.D˘a.t u = x, dv = cos 3xdx. Khi d´o du =1dx,v =1 3 sin 3x.T`u.d´oI = −1 3 x2cos 3x +2 3 1 3 x sin 3x −1 3 sin 3xdx= ... d´o du =11+x·dx2√x, v =2 3 x 3 2.Dod´oI =2 3 x 3 2arctg√x −1 3 x1+xdx=2 3 x 3 2arctg√x −1 3 1 −11+xdx=2 3 x 3 2arctg√x −1 3 (x −ln|1+x|)+C. V´ı du.2. ... 1916.dx 3 √x( 3 √x −1).(DS. 3 3√x + 3ln| 3 √x −1|)17.dx(1 −x2) 3/ 2.(DS. tg(arc sin x))Chı’dˆa˜n. D˘a.t x = sin t, t ∈−π2,π2)18.dx(x2+ a2) 3/ 2.(DS.1a2sinarctgxa)Chı’dˆa˜n....