%fsolve demo
%we'll solve the system of equations:
%x^2 + 2*y^2 = 3
%y = 5*x^2 + 6*x + 1
x = linspace(-1.75, 1.75, 1000);
y1 = ((3 - x.^2)./2).^(1/2);
y2 = -1 * ((3 - x.^2)./2).^(1/2);
y3 = 5.*x.^2 + 6.*x + 1;
plot(x,y1,'b');
hold on
plot(x,y2,'b');
plot(x,y3,'r');
%Here we are going to just use the default fsolve options.
%If we did not need to pass in x, we could just solve:
%fsolve(@myfun, y0)
%But in older versions of MATLAB we have to put something in the
%options field.
%So, OPTIONS = OPTIMSET (with no input arguments) creates an options structure
%OPTIONS where all the fields are set to [].
%initial guess for the vector y, get one solution
y0 = [1,1];
solution1 = fsolve(@myfun, y0, optimset)
%initial guess for the vector y, get the other solution
y0 = [-1, -1];
solution2 = fsolve(@myfun, y0, optimset)
y0 = [-1,1];
solution3 = fsolve(@myfun, y0, optimset)
plot(solution1(1),solution1(2),'go');
plot(solution2(1),solution2(2),'mo');
plot(solution3(1),solution3(2),'go');