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+--- Thread: Proper use of Solve App (/thread-4500.html)
Proper use of Solve App - ebswift - 08-09-2015 12:00 AM
I'm at a point where I'm horribly confused with the solve app. I can get it to work for different things, but there is one scenario where I'm finding it tough to get right - a simple solve for 2 unknowns. I tried a method from this thread, but get a cannot solve message:
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/forum.cgi?read=258059
Export attempt from above:
[attachment=2415]
symbolic view:
[attachment=2416]
Cannot solve:
[attachment=2417]
Now, the REALLY confusing part is that I got it working using X & Y variables. BUT, after playing with the l & w variables for a while I can't even get X & Y to solve anymore. I also mucked about using STO to no avail.
Please help with the solve workflow.
RE: Proper use of Solve App - Tim Wessman - 08-09-2015 01:03 AM
Are you up to date?
RE: Proper use of Solve App - ebswift - 08-09-2015 01:08 AM
Hi Tim, I believe so, same version on virtual and real calc:
[attachment=2418]
RE: Proper use of Solve App - rgallier - 08-09-2015 01:27 AM
I have found that clearing the variables will resolve this behavior (sometimes). Also delete the variables and re-export will work (sometimes). I'm very confused with the inconsistent behaviour.
RE: Proper use of Solve App - mandresve - 08-09-2015 03:03 AM
(08-09-2015 01:27 AM)rgallier Wrote: I have found that clearing the variables will resolve this behavior (sometimes). Also delete the variables and re-export will work (sometimes). I'm very confused with the inconsistent behaviour.
Same here =/
RE: Proper use of Solve App - Tim Wessman - 08-09-2015 03:23 AM
Do you see any problems if you enter any value other then "0" for your two guesses?
It seems to me the CAS fsolve command (which is what is being called in the solve app behind the scenes) is doing something strange when you put two guesses of 0 in. You can see this by typing this in the CAS screen.
fsolve([l = (w+10),(l*w) = 1200],[l,w])
Note that if you change that to a, b;
fsolve([a = (b+10),(a*b) = 1200],[a,b])
It works fine, and spits out the two results. If you store a float into the vars though of 0., using a:=0. b:=0. , you will start to see the misbehavior.
Store b:=.1, and suddenly it starts working again.
So I'd say put any number other then 0 in for a guess and it most likely will work. I think this might be something to go on Bernard's "list"...
RE: Proper use of Solve App - ebswift - 08-09-2015 03:49 AM
Yep, that's it, thanks Tim. Simply entering X: 1 Y: 1 in the guesses solves my example. It also works as expected with L and W.
When I originally solved it, I must have had values in there somehow.
RE: Proper use of Solve App - Tim Wessman - 08-12-2015 05:03 PM
Looks like Bernard actually fixed this a while back in the cas (after the last public release). It returns the vector of a result instead of the single number like I'd reported prior.
So when/if there is another release it should be resolved I think.