(1)∫ sin^3 x cos x dx =∫ sin^3 x dsinx =[(sinx)^4]/4+C (2)令[三次根号下(3x+1)]=t,则x=(t^3-1)/3 所以∫(x+1)/[x·3^√(3x+1)] dx=∫{[(t^3-1)/3+1]/[t(t^3-1)/3]}d[(t^3-1)/3] =∫t(t^3-1+3)/(t^3-1)dt=∫t[1...