On Fri, Oct 29, 2010 at 11:06 PM, Laurent <[email protected]> wrote: > sage: f(x)=sqrt(x)/( sqrt(4-x)-sqrt(4+x) ) > sage: f.limit(x=0) > Infinity > sage: limit(f,x=0) > Infinity > sage: f(0.0001) > -199.999999983591 > > A computation by hand shows that the limit is actually -Infinity. Why does > Sage say Infinity ?
"Infinity" in Sage represents the unsigned "complex" infinity, while "+Infinity" and "-Infinity" represent the real signed infinities. The limit is -Infinity only as you approach 0 from the positive side of the real axis: sage: limit(f, x=0, dir='plus') -Infinity As, you approach from the negative side of the real axis, you get complex infinity sage: f(-0.0001) 1.22464679904688e-14 + 199.999999983591*I sage: limit(f, x=0, dir='minus') Infinity Therefore, Sage (Maxima) says that the limit is complex infinity. --Mike -- To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
