10 HGR
15 HCOLOR=5
20 FOR T=0 TO 6.28 STEP 0.1
30 HPLOT COS(T) * 50 + 50, SIN(T) * 50 + 50 TO COS(T + 3.14) * 50 + 50, SIN(T + 3.14) * 50 + 50 
40 NEXT