dx ex4.计算广义积分 dx 0 Solution 十 1+x2J∞1+x2J01+x2 m .2 dr+lim s d x a→ a1+x lim larctanx lim larctanx b lim arctan a + lim arctan b b 2)2ex4. 计算广义积分 . 1  2 + − + x dx Solution.  + − + 2 1 x dx − + = 0 2 1 x dx  + + + 0 2 1 x dx  + = →−  0 2 1 1 lim a a dx x  + + →+  b b dx x 0 2 1 1 lim   0 lim arctan a a x →−  =   b b arctan x 0 lim →+  + a a lim arctan →−  = − b b lim arctan →+  + . 2 2 =    +       = − −