50 setheight
20 setxunit
-2 2 setyrange
-9.5 4 setxrange

/I {-3 0} def
/r 5 def

/I1 {I r 0 addv} def
/I2 {I r 0 subv} def

traceOx
xticks
xsubticks
xmarks
0 xtick
0 xmark

I times2
I I1 15 Arc
I I2 15 Arc