Try this:
syms x
y=(3/800)*((x).^2-(0.5)*((x).^4));
yv1 = fplot(y,[0 1]);
hold on
y1=(0.01/pi)*(((pi/2)*x*sin((pi/2)*x)+cos((pi/2)*x)-1));
yv2 = fplot(y1,[0 1]);
xlabel('y/l')
ylabel('uy/u')
hold off
yv = [yv1.YData; yv2.YData];
ymax = max(yv(:))
producing:
ymax =
1.8750e-003
.
