Please try this...
int RADIUS = 2;
float DEGREE_TO_RAD = 3.14 / 180;
glBegin( GL_LINE_LOOP );
glVertex2f( 0,0 );
int M_IN_DEGREE = 370;
int N_IN_DEGREE = 100;
for( int nR =N_IN_DEGREE; nR < M_IN_DEGREE; nR++ )
{
float fX = sin((float)nR * DEGREE_TO_RAD ) ;
float fY = cos((float)nR * DEGREE_TO_RAD );
glVertex2f( fX, fY );
}
glEnd();
With glDrawArrays
int M_IN_DEGREE = 370;
int N_IN_DEGREE = 100;
int nCount = 1;
float stVertexArray[2*360];
stVertexArray[0] = 0.0;
stVertexArray[1] = 0.0;
for( int nR =N_IN_DEGREE; nR < M_IN_DEGREE; nR++ )
{
float fX = sin((float)nR * DEGREE_TO_RAD ) ;
float fY = cos((float)nR * DEGREE_TO_RAD );
stVertexArray[nCount*2] = fX;
stVertexArray[nCount*2 + 1] = fY;
nCount++;
}
glEnableClientState( GL_VERTEX_ARRAY );
glVertexPointer( 2, GL_FLOAT, 0, stVertexArray );
glDrawArrays( GL_LINE_LOOP, 0, nCount );