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Full Version: 50g Multiple equation Solver (MES)
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I was reading about MES in the HP 50g User's Guide and tried the example of solving triangles ( page 7- 9) on my calculator. It worked fine but when I tried to solve a triangle problem, one of the sides was negative. The data:
a=20
alpha=45 degrees
betha=60 degrees

I press White key with left arrow and ALL
I press Orange key with right arrow and ALL

phi=75 degrees
b=24.49
c=-7.32

c must be positive.

Any suggestions?

Luis
(09-28-2017 03:21 PM)LGVE Wrote: [ -> ]I was reading about MES in the HP 50g User's Guide and tried the example of solving triangles ( page 7- 9) on my calculator. It worked fine but when I tried to solve a triangle problem, one of the sides was negative. The data:
a=20
alpha=45 degrees
betha=60 degrees

I press White key with left arrow and ALL
I press Orange key with right arrow and ALL

phi=75 degrees
b=24.49
c=-7.32

c must be positive.

Any suggestions?

Luis

The last value is comuputed probably from the cosine's law
C^2=A^2+B^2-2*A*B*cos(gamma)

Being quadratic, the solver might converge to either of the roots, with no easy way to persuade it to go the other way. One way is to provide initial guesses for A,B,C in the positive region (like 10). It might help it stay on the positive side but there's no guarantee.

So try again by setting B=10,C=10 as initial data, then solve for them too.
Setting b=10 c=10 and solving each variable individually works fine.
If I try to solve all variables at the same time using White key with left arrow and ALL and Orange key with right arrow and ALL, it doesn't work.

Luis
If you may be a frequent MES user, it might be worth fo you to check SolveSys49. The latter is more convenient than the HP50g stock MES for me, you get to the results in less time:

http://www.hpcalc.org/details/3145

Hope this helps.
Hi LGVE,
I had no problem using MES on my 50g.
I got b=24.49 c=27.32
So I started messing around putting numbers in b and c and that caused the 50g
to display c as a negative number (-7.)
I then went thru all the examples on page 7-17 and now it's working again.
I also ran MINIT from my home directory.
maybe a glitch in the software???

Try this out and see if it helps you.

Jim'
Hello,

unfortunately SolveSys49 does not handle units.

If you are looking for an easy way to handle the MES than GUIMES might come in handy.

Leaving a value in a field is treated as an initial guess, so if the solver might converge to a root that your are not looking for this can be used to point the solver in the right direction.

HTH,
Andreas
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