CAS diff() giving incorrect results
09-26-2021, 12:04 PM (This post was last modified: 09-26-2021 04:42 PM by Albert Chan.)
Post: #11
 Albert Chan Senior Member Posts: 1,676 Joined: Jul 2018
RE: CAS diff() giving incorrect results
I thought that expression|(x=a) notation can be simulated with eval(subst(quote(expression), x=a))
But, not quite. subst version is better ! (I skipped eval, because f(x) not defined)

CAS> 'integrate(f(x),x)' (x = t*t

integrate(f(t*t)*(t+t),t)

CAS> 'integrate(f(x),x, 1, 2)' (x = t*t

integrate(f(t*t)*(t+t),t, 1, √2)

CAS> integrate(f(x),x) |x = t*t

x*f(t^2)

CAS> integrate(f(x),x, 1, 2) |x = t*t

integrate(f(x),x, 1, 2)

---

I may have found a quoting bug. If quoted expression is saved to a variable, quote is gone.

CAS> assume( t >= 0)
CAS> m := 'integrate(1/(√x*(x+1)),x)' (x = t*t)

integrate(1/(√(t*t)*(t*t+1))*(t+t),t)

CAS> m // should have matched Ans

2*atan(t)

Update: another bug, if we use notation x = a .. b

CAS> 'integrate(f(x),x = 1 .. 2)' (x = t*t

integrate(f(t*t),(t*t) = (1 .. 2))
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 Messages In This Thread CAS diff() giving incorrect results - Wes Loewer - 09-22-2021, 07:10 PM RE: CAS diff() giving incorrect results - parisse - 09-22-2021, 07:26 PM RE: CAS diff() giving incorrect results - Wes Loewer - 09-23-2021, 06:20 PM RE: CAS diff() giving incorrect results - toml_12953 - 09-23-2021, 07:26 PM RE: CAS diff() giving incorrect results - Albert Chan - 09-24-2021, 10:48 AM RE: CAS diff() giving incorrect results - Wes Loewer - 09-24-2021, 04:28 PM RE: CAS diff() giving incorrect results - Albert Chan - 09-24-2021, 05:23 PM RE: CAS diff() giving incorrect results - Wes Loewer - 09-24-2021, 07:59 PM RE: CAS diff() giving incorrect results - parisse - 09-25-2021, 04:04 PM RE: CAS diff() giving incorrect results - Albert Chan - 09-25-2021, 05:03 PM RE: CAS diff() giving incorrect results - Albert Chan - 09-26-2021 12:04 PM

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