function shadecurves1(f, g, a, b)
%shadecurves takes strings or expressions f and g,
% interprets them as functions, plots them between
% x = a and x = b, and shades the region in between.
% Example: shadecurves1('sin(x)', '-sin(x)', 0, pi)
ffun = inline(vectorize(f)); gfun = inline(vectorize(g));
xvals = a:(b - a)/50:b;
plot([xvals, xvals], [ffun(xvals), gfun(xvals)])
