Cramers rule on a set of linear equations, notation help

In summary, the last line in the equation means that the coefficient for a11 is the determinant of the matrix M(6x6), which is the lead-in sequence.
  • #1
Missmk1
2
0

Homework Statement



I don't have a particular problem to solve, but I need help with understanding the notation I have found in an academic paper.

I have a system of linear equations which each take the form:

pi xi r1 + pi yi r2 - pi u + qi xi r4 + qi yi r5 - qi v + xi x + yi y - w/2 + mi = 0 (for i=1-6)


Where mi=((Li)^2- (xi)^2- (yi)^2- (pi)^2- (qi)^2 )/2

u=r1x+r2y+r3z
v=r4x+r5y+r6z
w= x^2+ y^2+ z^2

Where: pi, qi, xi, yi, Li and mi are all known quantities.

The paper outlines a method to solve for r1, r2, r4, r5, v, u, w, x, y, z


Homework Equations


The paper enters the equations into a 6 x10 matrix and called this matrix 'M'

The following equation then holds true:

M * t = 0

Where t is a 10 x 1 matrix

t = [r1; r2; u; r4; r5; v; x; y; z; 1]

(so all variables in the 'M' matrix are known and we are solving for the variables in the 't' matrix)

The paper then goes on to say that we can solve the system of equations symbolically using Cramer algorithm, regarding r1,r2,r4,r5,u,v as linear unknowns, and obtain the following expressions of those variables with respect to x,y,z.

a0r1 + a11x + a12y + a13w + a14 = 0
a0r2 + a21x + a22y + a23w + a24 = 0
a0u + a31x + a32y + a33w + a34 = 0
a0r4 + a41x + a42y + a43w + a44 = 0
a0r5 + a51x + a52y + a53w + a54 = 0
a0v + a61x + a62y + a63w + a64 = 0

Where

a0 = det(c1,c2,c3,c4,c5,c6)

And

aij = det(c1,...,ci-1,cj+6,ci+1,...,c6)


Now this is where I am getting stuck.

I am unsure of exactly what the last line of notation above means.


The Attempt at a Solution



I understand that a0 is equal to the determinant of the matrix 'M' when it is reduced to M(6x6).

But what exactly does the next line mean? I don't know how to calculate the coefficients aij.

If was looking for the coefficient a11 for instance would this constitute the following matrix:

aij = det(c1,...,ci-1,cj+6,ci+1,...,c6)
a11 = det(c1,..., c0,c7,c2,...,c6) ?

There is no column C0 is there? And I'm unsure of what columns of the matrix go into the two gaps.

Could somebody please help, I'm sure this must be relatively easy for somebody who works with this notation all the time, but I don't understand.

Thank you

MissMk1
 
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  • #2
Missmk1 said:
aij = det(c1,...,ci-1,cj+6,ci+1,...,c6)
a11 = det(c1,..., c0,c7,c2,...,c6) ?

There is no column C0 is there?
I can answer that part. In this case, it would simply mean that the lead-in sequence is empty:
a11 = det(c7,c2,...,c6)
 
  • #3
Thank you!

I think I understand it now

Thanks for your reply :)
 

What is Cramer's rule and how does it apply to a set of linear equations?

Cramer's rule is a method for solving systems of linear equations by using determinants. It is based on the fact that the solution to a system of linear equations can be expressed as a ratio of determinants.

How is Cramer's rule notated?

Cramer's rule is typically notated using the letter "D" for the main determinant, and the letters "Dx", "Dy", etc. for the determinants of the variables. The notation may also include subscripts to indicate the specific variable being solved for.

What are the steps for using Cramer's rule to solve a system of linear equations?

The steps for using Cramer's rule are: 1) Calculate the main determinant "D" by using the coefficients of the variables in the equations, 2) Calculate the determinants "Dx", "Dy", etc. by replacing the coefficients of the variable being solved for with the constant terms, 3) Solve for the variable by dividing the determinant "Dx", "Dy", etc. by the main determinant "D".

What are the advantages and limitations of using Cramer's rule?

The advantage of using Cramer's rule is that it provides a systematic and efficient method for solving systems of linear equations. However, it can be computationally intensive and may not work for systems with a large number of variables or equations.

Can Cramer's rule be used to solve non-linear equations?

No, Cramer's rule can only be used to solve systems of linear equations. Non-linear equations require different methods for solving, such as substitution or elimination.

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