math program????

scap1784 · Apprentice Joined: 25 Dec 2002 Posts: 225

My evil math professor decided to give us a problem that comes down to solveing a system of equations in which the system is 5 equations for 5 variables. I know how to do this on my claculator however my calculator is 35 min in to the problem and I am tired of looking at the little "busy" in the coner. Anyways I know linux is good for doing math computations and i was wondering if anyone knows of a program to get the answer to my problem. I have tired working it by hand and even my prof said good luck so i am just waiting now i guess.

Skip.za · Posted: Wed Jul 23, 2003 7:14 pm Post subject:

I would suggest using Octave. It's a Matlab compatible language and will have all matrix operations needed to solve linear equations.

odegard · Posted: Wed Jul 23, 2003 9:09 pm Post subject:

How far are you in math? 5 equations with 5 variables are childplay. 10 equations with 10 variables too. Do you know how to use a matrix? I don't remember exactly how atm but I could dig it up for you. Do it by hand, it will be faster.

Odegard

EDIT: Oh yeah, it has something to do with reducing the matrix. Hm...there was a method for this...arg, I don't remember the name, but it's simple!

Vanquirius · Posted: Wed Jul 23, 2003 9:19 pm Post subject:

SIR · Posted: Wed Jul 23, 2003 9:21 pm Post subject:

odegard · Posted: Wed Jul 23, 2003 9:49 pm Post subject:

daen1543 · Posted: Wed Jul 23, 2003 10:01 pm Post subject:

I don't think his calculator would take this long for a system of linear equations. Now, if those are 5 nonlinear equations, then yes, the system's a bitch to solve, unless you see a very clever solution.

Xargon · Posted: Thu Jul 24, 2003 2:12 am Post subject:

Are these algebraic or differential equations?
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Qubax · Posted: Thu Jul 24, 2003 2:21 pm Post subject:

partial differntial equations in 5 varialbes would be more interesting

pizen · Posted: Thu Jul 24, 2003 2:33 pm Post subject:

carambola5 · Apprentice Joined: 10 Jul 2002 Posts: 214

You guys are assuming that the system is a linear system. Maybe that's not the case. If it isn't a linear system, then your techniques will not work.

However, if it is a linear system, an easier way is to plug the matrix of coefficients into your calculator and take the inverse of the matrix. For example, with a 2-variable system:

ruronikenshin83 · n00b Joined: 25 Mar 2003 Posts: 42

Yea, if it's linear, definitely plug it into a matrix and do Gauss-Jordan, but do it by hand... it's the only way to learn. ^_^

I agree though, if it were five partial differential equations, it would be a lot more interesting. Although, you can still solve PDE's (as well as ODE's -- ordinary differential equations) using a matrix and doing Gauss-Jordan. Once again, assuming that the equations are linear.

asimon · Posted: Fri Jul 25, 2003 8:57 am Post subject:

I like MuPAD and used it during my Analysis classes. If you register you can get a free lisence for personal use. The program is like Maple or Mathematica.

dvink · n00b Joined: 12 Apr 2003 Posts: 55

Solutions to a set of linear equations Ax=y is very simple. First check whether the map x->Ax is "bijective", that is, "one-to-one and onto" , if so, then you can use elimination techniques to find the inverse A^-1. Do not use Cramers rule since it is highly inefficient!

spectatorion · n00b Joined: 12 Jul 2003 Posts: 35

GNU Octave is exactly what you're looking for (for Free). It issomething like a 90% clone of matlab, and it definitely has the capability for matrix computations, solving linear equations, and other linear algebra stuff.

references:
http://www.octave.org/doc/octave_2.html#SEC8 for entering a matrix (A is a 5x5 matrix, b is a 5x1 matrix)
http://www.octave.org/doc/octave_2.html#SEC10 for solving the system.

once you have the data entered, it should take less than a second to compute the result.

nngs · n00b Joined: 01 Oct 2002 Posts: 48

http://sal.kachinatech.com/sal1.shtml

Duck-Billed Platypus · Posted: Sun Jul 27, 2003 9:47 pm Post subject:

I'd just do it by hand, even if it takes a long time. I don't like to use calculators, unless they're not electronic, like abacuses and slide rules

. There's also the satisfaction of knowing that you actually did something.

I have a thing against electronic calculators, so I try not to use them, unless it's for the nice little graphics on my big fat graphing calculator my dad bought me about a year ago...
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odegard · Posted: Sun Jul 27, 2003 9:51 pm Post subject:

I have nothing against using my calculator which I bought for my own hard-earned cash through blood and tears.

It's a TI89 which I bought 6 years ago I think. Great!

scap1784 · Apprentice Joined: 25 Dec 2002 Posts: 225

First of all these aren't simple linear eq. They are all partial derivatives of V=BWH+y(BW+BH+WH-750)+u(B+W+H-50) I am trying to solve for the maxes and mins to find the maximum and minimum volume with the given constraints. Can that Octave prog do this??

shimage · n00b Joined: 18 Jul 2003 Posts: 48

scap1784 · Apprentice Joined: 25 Dec 2002 Posts: 225

V is a function for volume. There are two constraints on the volume so by useing Lagrange multipliers i came up with the above equation which my prof has said was right. The i come up with five equations by taking the partial derivitive of each of the variables. Then i set each of the equations equal to zero and try to solve for the variables to find the critical values.

Duck-Billed Platypus · Posted: Mon Jul 28, 2003 2:27 am Post subject:

I have no idea what you are talking about, but I'm sure that there is a way to do this by hand. I'd prefer doing it by hand, unless humungous calculations are involved, and then I'd use a calculator for that...
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odegard · Posted: Mon Jul 28, 2003 2:50 am Post subject:

What are the constraints? Too me it lookes like V=volum, B=breadth, H=height and L=length.

scap1784 · Apprentice Joined: 25 Dec 2002 Posts: 225

yea there is a way to do this by hand just bust out a multivarible calculus book and check out Lagrange multipliers and it will tell you how. I have tried it by hand but when it comes to trying to solve the system of equations i just can't do it. Now the constraints are that the rectangluar box has a surface area that is 1500 cm^2 and total edge length is 200 cm.

Qubax · Posted: Mon Jul 28, 2003 7:54 am Post subject:

can you post the indication of the problem?
i still don't understand the given problem really. maybe with some background ...
cause there is always more than one way to calculate something, maybe we can find a easier solution