OPTION ANGLE DEGREES
LET ABMAX=5
SET WINDOW -ABMAX,ABMAX,-ABMAX,ABMAX
DRAW grid(GRD(ABMAX/5),GRD(ABMAX/5))
DEF Xa(t)=4*COS(t)
DEF Ya(t)=4*SIN(t)
DEF Xb(t)=3*COS(t)
DEF Yb(t)=3*SIN(t)
DEF Xc(t)=3+COS(t)
DEF Yc(t)=SIN(t)
DEF X(t)=3*COS(t)+COS(-4*t)
DEF Y(t)=3*SIN(t)+SIN(-4*t)
FOR t=0 TO 360
   PLOT LINES: Xb(t),Yb(t);
NEXT T
PLOT LINES
SET LINE WIDTH 2
FOR t=0 TO 360
   PLOT LINES: Xa(t),Ya(t);
NEXT T
PLOT LINES
SET LINE COLOR 2
FOR t=0 TO 360
   PLOT LINES: Xc(t),Yc(t);
NEXT T
PLOT LINES
SET LINE COLOR 4
FOR t=0 TO 360
   PLOT LINES: X(t),Y(t);
NEXT T
PLOT LINES
DRAW DISK WITH SCALE(0.02*ABMAX)
SET COLOR 2
DRAW DISK WITH SCALE(0.01*ABMAX)*SHIFT(3,0)
SET COLOR 4
DRAW DISK WITH SCALE(0.02*ABMAX)*SHIFT(4,0)
END

EXTERNAL FUNCTION GRD(a)
LET KURAI=10^INT(LOG(a)/LOG(10))
LET B=INT(a/KURAI+0.5)
IF B=1 THEN LET Q=1
IF B=2 THEN LET Q=2
IF B>2 AND B<8 THEN LET Q=5
IF B=>8 THEN LET Q=10
LET GRD=Q*KURAI
END FUNCTION