This program is made by Bryan Mills, feel free to distribute and take credit if you 
want, I dont care!  


/START TI-81/
PRGM:  SMILE
:All-Off
:0->T                      -> is Sto> button
:"32+(sqrt)(30^2-(X-48)^2)"->Y1          (sqrt) square root 
:"38-(sqrt)(30^2-(X-48)^2)"->Y2           ^2 - squared button
:Lbl 5
:0->Z
:Lbl 1
:1->Xmin
:97->Xmax
:4.5->Ymin
:68.5->Ymax
:0->Yscl
:0->Xscl
:DispGraph
:PT-On(40,40
:PT-On(60,40
:Z+l->Z
:T+1->T
:PT-On(38,21
:PT-On(37,22
:PT-On(59,21
:PT-On(60,22
:PT-Off(38,19
:PT-Off(37,18
:PT-Off(59,19
:PT-Off(60,18
:Line(39,20,58,20
:If Z<10
:Goto 1
:Lbl 2
0->Z
Lbl 3
Z+1->Z
T+1->T
If T>1000                   Change the 1000 to fit how long you want it to run, or take it            
				out for infinite
Goto 9
PT-Off(38,21
PT-Off(37,22
PT-Off(59,21
PT-Off(60,22
:PT-On (38,21
:PT-On(38,19
:PT-On(37,18
PT-On(59,19
:PT-On(60,18
If Z<10
Goto 3
Goto 5
Lbl 9 
End
/End TI-81/