显然：lim(x→0+) arctan(1/x) =π/2lim(x→0-) arctan(1/x) = -π/2而：lim(x→0) [e^(1/x) +1]/[e^(1/x) -1]=lim(x→0) {1+[1/e^(1/x)]}/{1-[1/e^(1/x)]}=1因此，是跳跃间断点
