Math problem where graphing calculator may slow you down...
11-15-2014, 12:45 PM (This post was last modified: 11-15-2014 09:36 PM by Gilles.)
Post: #14
 Gilles Member Posts: 171 Joined: Oct 2014
RE: Math problem where graphing calculator may slow you down...
With HP50G,approx mode (but exact mode is OK):

Code:
'SIN(X)=COS(X)' SOLVEVX   { X 'LN(X)'}  Lsub   { n1 n n2 n } Lsub       SOLVEVX
here,you get :
Code:
{ 'X=EXP(6.2832*n-2.3562)'    'X=EXP(6.2832*n+0.7854)' }
Then you can test with some n values

Note that Lsub is a program I use for | (or SUBST) when equations are in a list (list processing don't work with | or subst) :
Code:
« 1 ->LIST  { | } + ->PRG MAP »

I also often use Lexr to get only the right part of equations in a list :
Code:
« 1 « EXLR NIP » DOSUBS »
Ex :
{ 'X=EXP(6.2832*n-2.3562)'
'X=EXP(6.2832*n+0.7854)' }
Lexr

gives

{ 'EXP(6.2832*n-2.3562)' 'EXP(6.2832*n+0.7854)' }

and for example to test n from -5 to 5, continue with

STEQ {}
-5 5 FOR a
EQ 'n' a 2 ->LIST Lsub +
NEXT
XNUM SORT

that gives

{ 2.1526E-15 4.9812E-14 1.1527E-12 2.6674E-11 6.1725E-10 1.4284E-8 3.3053E-7 7.6487E-6 0.0002 0.0041 0.0948 2.1933 50.7540 1174.4832 27178.3539 628925.9347 14553781.7413 336784589.923 7793428678.94 180345337617. 4.1733E12 9.6573E13 }

In exact mode you get

{ 'EXP(2*ATAN(-1+√2)-2*PI)' '1/EXP(2*ATAN(1+√2))' 'EXP(2*ATAN(-1+√2))' }

As you see the HP don't simplify the ATAN (but you can write easily your own program for trivial trig simplifications with a serie of MATCH commands. But it's not automatic and rather slow). I can post this if there is some intesrest

with the Prime

solve(sin(ln(x))=cos(ln(x)))

returns directly the symbolic simplified general solution... ( 'principal' uncheck in CAS setting)

It would fine if we could do :
equation | n={-1,0,1,2}
or
equation | n={-5...5}
to obtain a list of equations for each value.
But this dont work ....

So I do this:

Edit the general solution to change n_xxx by n
then
f(n):=ANS
concat(f(-1),f(0))
concat(ANS,f(1))
concat(ANS,f(2))
sort(ans)
~=
and you get the result (approx or exact)
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 Messages In This Thread Math problem where graphing calculator may slow you down... - CR Haeger - 08-14-2014, 02:08 PM RE: Math problem where graphing calculator may slow you down... - Thomas Klemm - 08-14-2014, 04:25 PM RE: Math problem where graphing calculator may slow you down... - CR Haeger - 08-14-2014, 04:36 PM RE: Math problem where graphing calculator may slow you down... - Thomas Klemm - 08-14-2014, 05:12 PM RE: Math problem where graphing calculator may slow you down... - Bunuel66 - 08-17-2014, 10:25 PM RE: Math problem where graphing calculator may slow you down... - CR Haeger - 08-18-2014, 03:10 PM RE: Math problem where graphing calculator may slow you down... - walter b - 08-18-2014, 03:41 PM RE: Math problem where graphing calculator may slow you down... - Thomas Klemm - 08-18-2014, 09:47 PM RE: Math problem where graphing calculator may slow you down... - Bunuel66 - 08-18-2014, 06:59 PM RE: Math problem where graphing calculator may slow you down... - aurelio - 08-18-2014, 09:34 PM RE: Math problem where graphing calculator may slow you down... - Bunuel66 - 08-18-2014, 10:26 PM RE: Math problem where graphing calculator may slow you down... - Thomas Klemm - 08-18-2014, 10:28 PM RE: Math problem where graphing calculator may slow you down... - Thomas Klemm - 08-18-2014, 10:52 PM RE: Math problem where graphing calculator may slow you down... - Gilles - 11-15-2014 12:45 PM

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