Differential equation plotting semicircle instead of circle?

Problem: (dy/dx) = (-x/y) , condition: y(sqrt(2)) = sqrt(2)

After solving equation on paper I got equation of a circle x^2 + y^2 = 4, but matlab plots a semicircle of radius 2. Why is this happening?

Code:

eqn='Dy=-x/y';

ini='y(sqrt(2))=sqrt(2)';

y=dsolve(eqn,ini,'x');

disp(y);

x=-2:0.1:2;

y1=eval(vectorize(y));

plot(x,y1)

[Torsten]

Two functions are solutions to your ODE:

y1(x)=sqrt(4-x^2) and y2(x)=-sqrt(4-x^2)

Since "dsolve" returns a function, not a relation as solution to your ODE, it will either return

y1(x) or y2(x).