How to plot a semi-circle?

How to plot a semi-circle and if I want just the curve of of the semi-circle and the radius of the circle is 500m?

Thanks

Answer 1

[Wayne King]

      theta = 0:.01:pi;
      y = 500*exp(1j*theta);
      plot(real(y),imag(y));
      axis([-750 750 -750 750]);
      grid on;

[Casey]

Thanks, but what if I want to slant the semicircle by 30 degree? is it possible?

[Dr. Seis]

theta = (0:.01:pi)+30*pi/180;

[Casey]

Thanks,If I want to shift the origin from (0,0) to (100,100)? Which command must I use?

[Elisabetta Di Franco]

This is very useful. I tried this but the semicircle is upsidedown and shifted. How can I change the code?