### Related

? identity;

Calculate

##### identity-matrix

q:matrix([a11,a12,a13...

d:identity(4);

Calculate

##### identity-matrix

A:matrix([.8,.1,.1],[...

A.A;

I:identity(3);

Calculate

kill(v1,v2,v2);

v1:[-1,0,1];

v2:[0,1,-1];

Calculate

? mode_identity;

Calculate

? identity;

Calculate

##### identity-matrix

q:matrix([a11,a12,a13...

d:identity(4);

Calculate

##### identity-matrix

A:matrix([.8,.1,.1],[...

A.A;

I:identity(3);

Calculate

kill(v1,v2,v2);

v1:[-1,0,1];

v2:[0,1,-1];

Calculate

? mode_identity;

Calculate

### identity

Run Example
```(%i1)A:matrix([.8,.1,.1],[.1,.7,.2],[.1,.1,.8]);
[ 0.8  0.1  0.1 ]
[               ]
(%o1)                          [ 0.1  0.7  0.2 ]
[               ]
[ 0.1  0.1  0.8 ]
(%i2) A.A;
[ 0.66  0.16  0.18 ]
[                  ]
(%o2)                        [ 0.17  0.52  0.31 ]
[                  ]
[ 0.17  0.16  0.67 ]
(%i3) I:identity(3);
(%o3)                                  3
(%i4) ```
Run Example
```sublist_indices ('[a, b, b, c, 1, 2, b, 3, b],                                 lambda ([x], x='b));
(%o1)                            [2, 3, 7, 9]
(%i2)  sublist_indices ('[a, b, b, c, 1, 2, b, 3, b], symbolp);
(%o2)                         [1, 2, 3, 4, 7, 9]
(%i3)  sublist_indices ([1 >
0, 1 <
0, 2 <
1, 2 >
1, 2 >
0],                                 identity);
(%o3)                              [1, 4, 5]
(%i4)  assume (x <
-1);
(%o4)                              [x < - 1]
(%i5)  map (maybe, [x >
0, x <
0, x <
-2]);
(%o5)                       [false, true, unknown]
(%i6)  sublist_indices ([x >
0, x <
0, x <
-2], identity);
(%o6)                                 [2]
(%i7) ```
Run Example
```n : matrix ([a[11], a[12]], [a[21], a[22]]);
[ a    a   ]
[  11   12 ]
(%o1)                            [          ]
[ a    a   ]
[  21   22 ]
(%i2) p_n : determinant (x . identity(2) - n), expand;
(%o2)     - 2 a   x + 2 a   x + 2 a   x - 2 a   x + a   a   - a   a
22        21        12        11      11  22    12  21
(%i3) at (p_n, [x = n]), expand;
[                                                  2  ]
[ - a   a   - a   a   + 2 a   a   + 2 a   a   - 2 a   ]
[    11  22    12  21      11  21      11  12      11 ]
(%o3)  Col 1 = [                                                     ]
[                            2                        ]
[ - 2 a   a   + a   a   + 2 a   + a   a   - 2 a   a   ]
[      21  22    11  22      21    12  21      11  21 ]
[                                      2              ]
[ - 2 a   a   + a   a   + a   a   + 2 a   - 2 a   a   ]
[      12  22    11  22    12  21      12      11  12 ]
Col 2 = [                                                     ]
[      2                                              ]
[ - 2 a   + 2 a   a   + 2 a   a   - a   a   - a   a   ]
[      22      21  22      12  22    11  22    12  21 ]
(%i4) ```

### Related Help

Help for Identity