### ap01_05.gnuplot
f(x) = sin(0.2*(x+4))*(x+2)
a = -5.0; b = -3.0
m = (f(b)-f(a))/(b-a) ## coeficiente angular da reta secante
P(x) = f(a) + m*(x-a)
## plot f(x), P(x),0
## print f(-4), P(-5)
set xrange [-6:-2]
set terminal postscript portrait enhanced
set output "ap01_05.eps"
plot f(x), P(x),0
print f(-4),  (a  - f(a)/m), f(-4) - f(a - f(a)/m)