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+--- Thread: bug xCas limit (/thread-16993.html)
bug xCas limit - robmio - 05-23-2021 11:41 AM
Hi everyone, maybe I discovered a bug in xCas: the following limit results in "zero" instead of "-1":
limit (cos (x) / (x-pi / 2), x = pi / 2)
Try to calculate it both with "HP PRIME" and with Giac xCas.
Best regards, Roberto
RE: bug xCas limit - Albert Chan - 05-23-2021 05:31 PM
For XCas, replacing variable x to others seems to help.
XCas> f(a) := limit(cos(t+pi/2-a)/(t-a), t=a)
XCas> f(pi/2) → -1
XCas> f(pi/3) → -1
XCas> f(0) → -1
Cas> f(a) := limit(cos(t+pi/2-a)/(t-a), t=a)
Cas> f(pi/2) → 0
Cas> f(pi/3) → 0
Cas> f(0) → -SIN(a)/a ???
RE: bug xCas limit - Albert Chan - 08-12-2021 12:03 AM
Another XCas limit bug (for HP Prime Cas, limit crashes)
XCas> asinh(x) → ln(x+sqrt(x^2+1))
XCas> asinh(i) → ln(i) = ln(abs(i)) + i*arg(i) = i*pi/2
XCas> limit(asinh(i*x), x=1)
"Limit: Max order reached or unable to make series expansion Error: Bad Argument Value"
Udpate Nov 10,2022:
I upgraded to XCas 1.9.0-22 (win32).
OP bug now fixed. However, asinh limit bug remain.
XCAS> limit (cos(x)/(x-pi/2), x = pi/2) → -1