SET WINDOW -11,11,-11,11
FOR Q=1 TO 2
   FOR x=0 TO 2*PI STEP 0.005
      IF x < PI/2 OR x > PI*3/2 THEN 
         SET COLOR 21
      ELSE 
         SET COLOR 28
      END IF
      SET DRAW MODE hidden
      CLEAR
      PLOT AREA: 0,-5;10*COS(x),-5;10*COS(x),5;0,5
      SET COLOR 1
      SET LINE WIDTH 3
      PLOT LINES: 2*COS(x),-2;8*COS(x),0;2*COS(x),2;2*COS(x),-2
      PLOT LINES: 0,-7;0,7    
      WAIT DELAY 0.005
      SET DRAW MODE explicit
   NEXT x
NEXT Q
END