Basic Examples

In[]:=
Find the matrix of cofactors of an input matrix:
[◼]
CofactorMatrix
[{{3,2,5},{4,3,-1},{2,3,4}}]
In[]:=
{{15,-18,6},{7,2,-5},{-17,23,1}}
Out[]=
The identity matrix is equal to its own cofactor matrix:
[◼]
CofactorMatrix
[{{1,0},{0,1}}]
In[]:=
{{1,0},{0,1}}
Out[]=
Find the matrix of cofactors of another matrix:
[◼]
CofactorMatrix
[{{3,0,2},{2,0,-2},{0,1,1}}]
In[]:=
{{2,-2,2},{2,3,-3},{0,10,0}}
Out[]=
Find the cofactor matrix of a matrix having symbolic elements:
[◼]
CofactorMatrix
[{{1,1,1},{a^2,a,1},{b^2,b,1}}]
In[]:=
a-b,-a
2
+b
2
,a
2
b-ab
2
,-1+b,1-b
2
,-b+b
2
,{1-a,-1+a
2
,a-a
2
}
Out[]=

Scope

CofactorMatrix returns unevaluated for non-square matrix input:
[◼]
CofactorMatrix
[Sin[x]]
In[]:=
[◼]
CofactorMatrix
[Sin[x]]
Out[]=
[◼]
CofactorMatrix
[{{3,0},{2,0},{0,1}}]
In[]:=
[◼]
CofactorMatrix
[{{3,0},{2,0},{0,1}}]
Out[]=