lor="#82140F">
show "First 2 terms of perturbation expansion"
set y axis name horizontal
set y name "sea-level"
set x name "$\omega$t"
<p>
\b = "0.4" # perturbation parameter b=dH/H
\xmin = "0"
\xmax = "6.28"
\xinc = "3.14 / 20"
\function = "cos(x)"
set x axis \xmin \xmax
create columns from function
draw curve
draw title "SOLID LINE  \function"
<p>
\function = "(cos(x)+\b/2*(1-cos(2*x)))"
create columns from function
set dash 1
draw curve
draw title "DASHED LINE \function"
<p>
draw title "b = \b"
</font></