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Taylor Expansion not working
08-14-2015, 05:38 PM
Post: #1
Taylor Expansion not working
Hello,
I have been a long time user of the 48SX and GX and just got a 50g to replace the SX.

So....and now I want to do a taylor expansion of sqrt(0.2*x+1)
So...first when i assemble the root is asks me to turn on approx mode - OK
I put on the stack
> sqrt(etc)
>'X'
>5

and i get the message: "Approx mode off"
...OK...
Next it s pop-up: "TAYLR error: Mode switch not allowed here "

hmmmmm.....works on the SX. Can someone give me a hint how to do that?

Wolfram
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08-14-2015, 06:54 PM (This post was last modified: 08-14-2015 06:56 PM by Gerson W. Barbosa.)
Post: #2
RE: Taylor Expansion not working
Try replacing 0.2*X with X/5
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08-14-2015, 07:25 PM
Post: #3
RE: Taylor Expansion not working
(08-14-2015 06:54 PM)Gerson W. Barbosa Wrote:  Try replacing 0.2*X with X/5

Ok, this equation was just an example ..i actually need (0.000231*x+0.1296480889)^0.5
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08-14-2015, 08:33 PM
Post: #4
RE: Taylor Expansion not working
(08-14-2015 07:25 PM)wneff Wrote:  
(08-14-2015 06:54 PM)Gerson W. Barbosa Wrote:  Try replacing 0.2*X with X/5

Ok, this equation was just an example ..i actually need (0.000231*x+0.1296480889)^0.5

In exact mode,

'√(231/1000000*X+1296480889/10000000000)'
'X'
3
TAYLR

-->

'5788125000*√1296480889/1637269993841868597755699*X^3-55125*√1296480889/13891427235886201*X^2+21*√1296480889/2357237980*X+√1296480889/100000'

You might need to set flag -79 (Textbook off).

HTH,

Gerson.
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08-14-2015, 09:37 PM
Post: #5
RE: Taylor Expansion not working
(08-14-2015 08:33 PM)Gerson W. Barbosa Wrote:  
(08-14-2015 07:25 PM)wneff Wrote:  Ok, this equation was just an example ..i actually need (0.000231*x+0.1296480889)^0.5

In exact mode,

'√(231/1000000*X+1296480889/10000000000)'
'X'
3
TAYLR

-->

'5788125000*√1296480889/1637269993841868597755699*X^3-55125*√1296480889/13891427235886201*X^2+21*√1296480889/2357237980*X+√1296480889/100000'

You might need to set flag -79 (Textbook off).

HTH,

Gerson.

Super that worked! Thanks a lot. Now - this seems weird to me that it can't just give me the polynomila numbers as decimals - is there a way to chenage settings to get that done?
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08-17-2015, 05:16 PM
Post: #6
RE: Taylor Expansion not working
Hello,

I believe you can use the ->Q command under the Convert>Rewrite menu to do the conversion from decimal to fractional automatically, at least it seems to be working on your example, giving

Code:
sqrt(1/4329*X+129/995)

After that you could perform the Taylor expansion.

Hope this help.
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