# Tick Marks and Intercepts

Help! I'm trying to use Sage to plot x-intercepts, and there seems to be a problem when I try to zoom in too far. E.g. if I execute

plot(1-4*x^2,.4999,.5001,tick_formatter=.0001.n(digits=6))

then I get exactly what I expect, but if I execute

plot(1-4*x^2,.49999,.50001,tick_formatter=.00001.n(digits=7))

then I get this error message:

Traceback (click to the left of this block for traceback) ... Unknown symbol: \verb (at char 0), (line:1, col:1)

Curiously, this seems to be directly related to the fact that my function is crossing the x axis on the domain in question. E.g. if I try

plot(1-4*x^2,1.49999,1.50001,tick_formatter=.00001.n(digits=7))

then everything comes out fine.

Any thoughts on what's going on and/or how to get around it?

Thanks.