1. is Orthogonal Matrix ?
`[[0,1],[1,0]]`
Solution:
A square matrix `A`, such that `A xx A^T = I`, is called an orthogonal matrix, where `I` is an identity matrix and `A^T` is the transpose of matrix `A`.
= | | `0×0+1×1` | `0×1+1×0` | | | `1×0+0×1` | `1×1+0×0` | |
|
`A xx A^T = I`, So `A` is an orthogonal matrix
2. is Orthogonal Matrix ?
`[[4,-3,1],[0,11,-5],[6,9,14]]`
Solution:
A square matrix `A`, such that `A xx A^T = I`, is called an orthogonal matrix, where `I` is an identity matrix and `A^T` is the transpose of matrix `A`.
`A` | = | | `4` | `-3` | `1` | | | `0` | `11` | `-5` | | | `6` | `9` | `14` | |
|
`A^T` | = | | `4` | `-3` | `1` | | | `0` | `11` | `-5` | | | `6` | `9` | `14` | |
| T |
| = | | `4` | `0` | `6` | | | `-3` | `11` | `9` | | | `1` | `-5` | `14` | |
|
`A×(A^T)` | = | | `4` | `-3` | `1` | | | `0` | `11` | `-5` | | | `6` | `9` | `14` | |
| × | | `4` | `0` | `6` | | | `-3` | `11` | `9` | | | `1` | `-5` | `14` | |
|
= | | `4×4-3×-3+1×1` | `4×0-3×11+1×-5` | `4×6-3×9+1×14` | | | `0×4+11×-3-5×1` | `0×0+11×11-5×-5` | `0×6+11×9-5×14` | | | `6×4+9×-3+14×1` | `6×0+9×11+14×-5` | `6×6+9×9+14×14` | |
|
= | | `16+9+1` | `0-33-5` | `24-27+14` | | | `0-33-5` | `0+121+25` | `0+99-70` | | | `24-27+14` | `0+99-70` | `36+81+196` | |
|
= | | `26` | `-38` | `11` | | | `-38` | `146` | `29` | | | `11` | `29` | `313` | |
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`A xx A^T != I`, So `A` is not an orthogonal matrix
This material is intended as a summary. Use your textbook for detail explanation.
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