十 +xd=)(x--)2+2 +oO 1.x,、,兀 arctan 22 2 2 元 2、2 K心dx x x x  + + + = 0 2 2 2 1 1 1  + − + − = 0 2 ) 2 1 ( ) 1 ( x x x d x 2 0 1 arctan 2 1 +  − = x x 2 )] 2 ( 2 [ 2 1    = − − = . 2 2  I =