tan't -sec2 tdt -∫eos,iast-jd-7uosi cost+ 1 cost 3.含√x2-a2型(a>0) V1+x2 方法：令x=secl,i∈(0，) 88 3 3 2 2 3 2 3 tan sec (1 ) (1 tan ) x t dx tdt x t = + +   3 2 sin cos t dt t =  2 2 sin cos cos t d t t = − 2 2 cos 1 cos cos t d t t − =  2 1 (1 ) cos cos d t t = −  2 2 1 1 cos 1 cos 1 t c x c t x = + + = + + + + 3．含 2 2 x a − 型( 0) a  方法：令 sec , (0, ) 2 x a t t  =  t x 2 1+ x 1