Register to reply 
Inverse of a matrix + determinant 
Share this thread: 
#1
Sep3011, 02:09 AM

P: 140

To determine if a matrix is invertible or not, can we determine this by seeing if the determinant of the matrix is zero or nonzero ?
If it's zero, then the matrix doesn't exist because the inverse of the determinant would be an infinite number ? 


#2
Sep3011, 04:28 PM

Engineering
Sci Advisor
HW Helper
Thanks
P: 6,953

You need to be careful about how you use the word "infinite" in mathematics, but your basic idea is right. 


#3
Sep3011, 09:31 PM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,340

A reason for that is that the inverse of an invertible matrix is the matrix in which the "ij" term is the minor of the "ji" term of the original matrix divided by the determinant. Given an "ji" term, it has a minor so the only problem is that we cannot divide by 0.



#4
Sep3011, 11:50 PM

P: 662

Inverse of a matrix + determinant
Another way of looking at it (for nxnmatrices):
Det(AB)=DetADetB; In our case, say we have an inverse A' for A, then: AA'=I , so that, Det(AA')=DetADetA'=DetI=1, So you need two numbers whose product equals one, and that rules out DetA=0. 


Register to reply 
Related Discussions  
NxNcomplex matrix, identified 2Nx2Nreal matrix, determinant  Linear & Abstract Algebra  2  
Finding determinant given determinant of another matrix  Calculus & Beyond Homework  3  
Frechet (second) derivative of the determinant and inverse functions  Calculus & Beyond Homework  1  
Matrix pseudoinverse to do inverse discrete fourier transform  Linear & Abstract Algebra  3  
Matrix/Determinant/Inverse Q's  Linear & Abstract Algebra  3 