8)「21,2l=1 arctan x+C afx (19)-,1,d +c 2 2 2a x+a (20)」2 a2:2v= 1 a+x+ 2a a-x (21) 仄x= arcsin+C 2 (22)r x4、dx=lnx+Vx2±a2+CC a x a dx a x = + +  arctan 1 1 (18) 2 2 C x a x a a dx x a + + − = −  ln 2 1 1 (19) 2 2 C a x a x a dx a x + − + = −  ln 2 1 1 (20) 2 2 C a x dx a x = + −  arcsin 1 (21) 2 2 dx x x a C x a = +  +   2 2 2 2 ln 1 (22)