Re: Solving nonrational expressions on 49G? Message #7 Posted by Karl Schneider on 17 June 2008, 1:30 a.m., in response to message #2 by Arnaud Amiel
Equation to solve, using the HP49:
((40000*A+4000)/exp(A))=5000
which simplifies to
40*A  5*exp(A) + 4 = 0
whose derivative is
40  5*exp(A)
Solving that for zero yields A = ln(8) ~= 2.079441542.
This is the inflection point for the initial guess that determines which solution the HP15C gives, but not on the HP49G.
Quote:
the numeric solver [RS][7] gives the following answer straight away A=2.863E2
You can also use ROOT which gives the same answer with a guess of 0. But a different answer with a guess of 2.
The "different" (but still valid) answer is 3.30455610804.
My difficutly was figuring out how to copy 'n' paste the expression into the "NUM.SLV" form after symbolic solution "S.SLV" failed. I finally saved it to a variable and loaded that using "CHOOSE".
(Sigh.) Once again, I would have had my answers so much faster with an ancient HP34C or HP15C, despite the vast difference in computational speed.
 KS
Edited: 17 June 2008, 1:56 a.m.
