#1846 closed defect (invalid)
maxima looses minus signs in symbolic expression
Reported by: | jkantor | Owned by: | was |
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Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |
Component: | calculus | Keywords: | |
Cc: | Merged in: | ||
Authors: | Reviewers: | ||
Report Upstream: | Work issues: | ||
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description
Consider
log(a*e^(-a*x-b)).simplify_exp()
This gets expanded correctly, however
log(a*e^(-a*x-b)/(1+exp(-a*x-b))^2 ).simplify_exp()
appears to lose the minus signs on ax and b.
Change History (3)
comment:1 Changed 12 years ago by
- Resolution set to invalid
- Status changed from new to closed
comment:2 Changed 12 years ago by
- Milestone set to sage-2.10.1
comment:3 Changed 12 years ago by
- Milestone changed from sage-2.10.1 to sage-duplicate/invalid
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Actually Sage is right and you are wrong, because of the identity
log(e^(-a*x - b) + 1) == log(e^(a*x + b) + 1) - a*x - b
which one can derive from Taylor expansions oflog(x+1)
andlog(x^(-1) + 1)
. See below.