% Problem # 12 (or Fichtenholz's Function # 2)
% Range of initial points: 0 <= x <= 2*pi
% Two global maximum: x={pi,3*pi/2}
% f(x)=1
% Coded by: Ali R. Alroomi | Last Update: 25 Feb. 2015 | www.al-roomi.org
 
clear
clc
warning off
 
xmin=0;
xmax=2*pi;
R=100000; % steps resolution
x=xmin:(xmax-xmin)/R:xmax;
 
for i=1:length(x)
    f(i)=-(sin(x(i)))^3-(cos(x(i)))^3;
end
 
plot(x,f,'r','LineWidth',2);grid;set(gca,'FontSize',12);
xlabel('x','FontName','Times','FontSize',20,'FontAngle','italic');
ylabel('f(x)','FontName','Times','FontSize',20,'FontAngle','italic');