GLE Example: lnx.gle

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---

size 9 7

include "shape.gle"
include "graphutil.gle"

a = 4

! draw graph
set texlabels 1
begin graph
   scale auto
   title "Natural Logarithm"
   xtitle "$x$"
   ytitle "$y$"
   xaxis min 0 max a+1
   yaxis min 0 max 1.2
   let d1 = 1/x
   let d2 = 1/x from 1 to a
   d1 line color red
   fill x1,d2 color moccasin
end graph

! draw vertical red lines
set color red
graph_line 1 0 1 1
graph_line a 0 a 1/a
set color black

! draw integral equation
set just cc
amove xg(2.5) yg(0.18)
tex "$\displaystyle\log a = \int_{1}^{a}{\textstyle \frac{1}{x}\,dx}$"

! define subroutine to add labels to graph
sub label_by_dist_angle xp yp label$ dist angle
   default dist 0.75
   default angle 90
   amove xg(xp) yg(yp); pmove dist angle
   set just bc; tex label$
   amove xg(xp) yg(yp); pmove dist-0.1 angle
   aline xg(xp) yg(yp) arrow end
end sub

! draw "a" and "1/x"
label_by_dist_angle a    1/a    "$a$"
label_by_dist_angle 1.75 1/1.75 "$y = \frac{1}{x}$" angle 40

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