set term post enh
set out "hyperb.ps"
set xlabel "s"
set ylabel "{/Symbol k}, {/Symbol t}"
plot [s=-5:5] [0:6] sqrt(1+s**2) title "{/Symbol k}", \
   abs(s) title "asymptote for {/Symbol k}", \
  .9/(1 + s**2) title "{/Symbol t}" lt 1