Question: how to deal with these warning?

April 27 2012 ZhuWeihong 15
Maple 16

0

i study a simple differential equations as follow and get the solution,but i faced two warning which puzzle me:

> restart;
> eq2 := diff(x(t), t) = x(t), diff(y(t), t) = x(t)^2+y(t)^2-1;
   ans1 := dsolve({eq2, x(0) = 1, y(0) = -1}, numeric, [x(t), y(t)], range = -10 .. 10)       ;

Warning, cannot evaluate the solution further left of -1.1646698, probably a singularity
Warning, cannot evaluate the solution further right of 1.3617090, probably a singularity        

this differential     equation has two critical point:(0,1),(0,-1)

but the warnings show cannot evalue the solution ..., probably a singularity?   they are vital for my solution?  i cant ge the sulution at point t=1.3617, so how to deal with this warning? thank you...

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