估计下列各积分的值:-|||-(1) (int )_(1)^4((x)^2+1)dx;-|||-(2) (int )_(dfrac {pi )(4)}^dfrac (5{4)pi }(1+(sin )^2x)dx;-|||-(3) (int )_(dfrac {1)(sqrt {3)}}^sqrt (3)xarctan xdx;-|||-(4) (int )_(2)^0(e)^(x^2)-xdx.