Rotate an ellipse

I need to rotate an ellipse, my code to draw it is:

double const TWO_PI = 6.2831853071795865;
int const NSTEPS = 100;
double t = 0;
glBegin( GL_LINE_LOOP );
for ( int i = 0; i < NSTEPS; ++i )
{
glVertex2d( 0.5 * cos( t ), 0.5 * sin( t ) );
t += TWO_PI / NSTEPS;
}
glEnd();

Now, how do i rotate it???

Check the function glRotate…

does glRotatef not work?

In anticipation of your next problem… Since the scale values for both X and Y are .5, you are going to get a circle with a radius of .5 and rotating it will do nothing, of course.