math /xrange=-3:3
margin 0.03
plot exp(-x**2)
l = $(eval 'sqrt(log(2.0))')
draw-line -$(l),0.5 $(l),0.5 /line-style Dashes
draw-text 0,0.3 'Half height width: $w = \sqrt{\ln 2}$' /text-width=3cm