10 SYS 37173,"0",-5,5,-5*0.625
20 :
30 FOR A=3 TO 1 STEP -0.5
40 : SYS 37173,"+SQR(A*A-X*X)"
50 : SYS 37173,"-SQR(A*A-X*X)"
60 NEXT A
70 :
80 POKE 198,0:WAIT198,1:GETZ$
90 SYS 40211