# Can FX115 solve Simultaneous Equations



## BamaBino (Aug 25, 2010)

Can the Casio FX115 solve Simultaneous Equations with Complex constants?

such as

(1 + j6) I1 - j6 I2 = 16 /-40

-jI1 + (2 + j4) I2 = 0

these are the 2 equations and I1 and I2 are the 2 unknowns.

Thanks.


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## Wildsoldier PE (Aug 25, 2010)

BamaBino said:


> Can the Casio FX115 solve Simultaneous Equations with Complex constants?
> such as
> 
> (1 + j6) I1 - j6 I2 = 16 /-40
> ...



I think that the casio cant solve simult. equations with complex numbers. What you can do is do it by hand. If it is 2 unknowns you can solve for I1= on first equation so that the I1 are in terms of I2. and then substitute I1=I2blabla bla bla on the second equation. Then equation 2 will all be in terms of I2...solve for I2 and then substituted the I2 value on equation I1=I2 bla bla bla. I hope you understand what i mean. Is kind of confusing but is the best way i found when is only 2 unknowns.


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## BamaBino (Aug 25, 2010)

Wildsoldier said:


> I think that the casio cant solve simult. equations with complex numbers. What you can do is do it by hand. If it is 2 unknowns you can solve for I1= on first equation so that the I1 are in terms of I2. and then substitute I1=I2blabla bla bla on the second equation. Then equation 2 will all be in terms of I2...solve for I2 and then substituted the I2 value on equation I1=I2 bla bla bla. I hope you understand what i mean. Is kind of confusing but is the best way i found when is only 2 unknowns.


Thanks for the reply. I know how to do it by hand.

But it would be SWEET if I could just plug-in the complex numbers directly and get the answers (and then go to the next problem).

This would be a deal breaker for me if one calculator could do this and the others couldn't.

Does anybody else knew if any of the approved calculators can solve simultaneous equations with complex numbers?

NCEES acceptable calculators:

Casio:

* fx-115 MS

* fx-115 MS Plus

* fx-115 MS SR

* fx-115 ES

Hewlett Packard:

* HP 33s

* HP 35s

Texas Instruments:

* TI-30Xa

* TI-30Xa SOLAR

* TI-30Xa SE

* TI-30XS Multiview

* TI-30X IIB

* TI-30X IIS

* TI-36X II

* TI-36X SOLAR

last updated: Nov. 16, 2009

next update: Nov. 15, 2010

Thanks a bunch!


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## DK PE (Aug 25, 2010)

BamaBino said:


> Wildsoldier said:
> 
> 
> > I think that the casio cant solve simult. equations with complex numbers. What you can do is do it by hand. If it is 2 unknowns you can solve for I1= on first equation so that the I1 are in terms of I2. and then substitute I1=I2blabla bla bla on the second equation. Then equation 2 will all be in terms of I2...solve for I2 and then substituted the I2 value on equation I1=I2 bla bla bla. I hope you understand what i mean. Is kind of confusing but is the best way i found when is only 2 unknowns.
> ...


Understand your concern as it looks like a mesh equation with some R's and L's.... but it's been stated here often... pick whatever calculator you feel most comfortable with that is on the list and toss away anything else until after the exam... balance your checkbook, do your studying problems, force yourself to use it at work, home, everywhere. In my opinion, effort figuring out how to use your calculator to solve simultaneous equations with complex coefficients would be better off put towards convert rect--&gt; polar and back quickly and accurately, knowing your references and other operations at the same level. Just my $0.02 worth


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## wilheldp_PE (Aug 25, 2010)

Keep in mind that the exam problems are designed to be solved in 6 minutes or less. I seriously doubt you will have the need to solve simultaneous complex equations to get a solution on the FE or PE.


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## BamaBino (Aug 25, 2010)

DK PE said:


> pick whatever calculator you feel most comfortable with that is on the list and toss away anything else until after the exam... balance your checkbook, do your studying problems, force yourself to use it at work, home, everywhere.


I totally agree with that. I'm evaluating which one I want to use, then have 2 of the same type (one at home and one at work). I currently have a FX155ES and a HP33.



DK PE said:


> better off put towards convert rect--&gt; polar and back quickly and accurately, knowing your references and other operations at the same level. Just my $0.02 worth


The FX115 does that really well.

But it would be SWEET if I could just plug-in the complex number to solve simultaneous equations.


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## sparky2010 (Aug 27, 2010)

I don't know if the FX115 can solve for complex polynomial solutions, but the HP-33S cannot unless you load the program from this site to solve a third order complex equation:

http://www.hpmuseum.org/cgi-sys/cgiwrap/hp...es.cgi?read=722

I prepared to see such a problem when I took the exam, but it was absent. Likely they think it would be too time consuming to crunch the numbers by hand so they exclude it from consideration.

cheers,

Len


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## BamaBino (Aug 31, 2010)

BamaBino said:


> But it would be SWEET if I could just plug-in the complex number to solve simultaneous equations.


Ok, last week I got the 2009 NCEES sample problems book and it appears that solving simultaneous equations with complex coefficients will not required.

I'm trying to like the fx-115ES; the equation editing feature is nice.

_But_ I don't like that "calculation history memory contents are cleared whenever the calculator is turned off, ON key is pressed, change to calculation mode or the input/output format, or perform any reset operation."


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## wilheldp_PE (Aug 31, 2010)

BamaBino said:


> Ok, last week I got the 2009 NCEES sample problems book and it appears that solving simultaneous equations with complex coefficients will not required.


Told ya so.


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## BamaBino (Sep 6, 2010)

I was at Target today and they have dropped the price on the fx115ES to $13.09


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