[CRASH] plotfunc() fails
06-21-2014, 05:01 PM (This post was last modified: 06-21-2014 05:03 PM by alexzkter.)
Post: #1
 alexzkter Member Posts: 64 Joined: Apr 2014
[CRASH] plotfunc() fails
I'm trying to get all answers from a Van Der Waals cubic equation.

Here's the definition of variables:

I defined 'x' too (x:=0)

When trying to plot the following equation on CAS, the hourglass stays there forever.

Which doesn't happen on it's equivalent form, the standard cubic form:

Anyway, I just managed to get all 3 answers from both forms of my equation.
There are 4 ways to solve the equation, by using the following sintaxis:
• With solve
solve(equation,var)
solve({equation},{var}) For multiple equations.
• With fsolve
fsolve(equation,var)
fsolve([equation],[var])--> For multiple equations, but this one only shows 1 result in my case.
06-22-2014, 05:54 AM (This post was last modified: 06-22-2014 07:06 AM by parisse.)
Post: #2
 parisse Senior Member Posts: 1,036 Joined: Dec 2013
RE: [CRASH] plotfunc() fails
Can you write your equations in plain text instead of a screenshot?
Like this
P:=7000000.; R:=8.314; T:=423.15; Tc:=369.8; Pc:=41.9*101325;
a:=27*R^2*Tc^2/64/Pc; b:=R*Tc/8/Pc;
plotfunc(R*T/(x-b)-a/x^2-P)
It's much more efficient, because anyone can check quickly by doing a copy/paste, and you are certain we check with the right data.
I just checked on the emulator, it works.
06-22-2014, 10:01 AM (This post was last modified: 06-22-2014 10:04 AM by alexzkter.)
Post: #3
 alexzkter Member Posts: 64 Joined: Apr 2014
RE: [CRASH] plotfunc() fails
(06-22-2014 05:54 AM)parisse Wrote:  Can you write your equations in plain text instead of a screenshot?
Like this
P:=7000000.; R:=8.314; T:=423.15; Tc:=369.8; Pc:=41.9*101325;
a:=27*R^2*Tc^2/64/Pc; b:=R*Tc/8/Pc;
plotfunc(R*T/(x-b)-a/x^2-P)
It's much more efficient, because anyone can check quickly by doing a copy/paste, and you are certain we check with the right data.
I just checked on the emulator, it works.

Yes, I'll do that next time.
I typed in plotfunc(R*T/(x-b)-a/x^2-P) on a note, copy-pasted it on CAS and I still get the hourglass. Even if a and b are declared as you did.
06-22-2014, 02:35 PM
Post: #4
 parisse Senior Member Posts: 1,036 Joined: Dec 2013
RE: [CRASH] plotfunc() fails
If it does not work on your version of the emulator, and it works on mine, then it probably means some bug has been fixed.
06-22-2014, 06:11 PM (This post was last modified: 06-22-2014 06:12 PM by alexzkter.)
Post: #5
 alexzkter Member Posts: 64 Joined: Apr 2014
RE: [CRASH] plotfunc() fails
(06-22-2014 02:35 PM)parisse Wrote:  If it does not work on your version of the emulator, and it works on mine, then it probably means some bug has been fixed.

I have the latest Rev.6031 ...
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