# Checker functions for orthogonality of coordinate system #12882

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merged 4 commits into from Jul 5, 2017

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### szymag commented Jul 3, 2017

 This PR introduce additional condition for transformation equation which must be fulfill. In `vector` module we are dealing with orthogonal curvilinear coordinate system only, so we need to check if transformation equations are correctly defined. Closes #12852
``` Add checker function for orthogonality of creating coordinate system. ```
``` d32e42d ```
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### szymag commented Jul 3, 2017

 ping @Upabjojr
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### Upabjojr commented Jul 3, 2017

 Need tests.

### szymag added some commits Jul 3, 2017

``` Add checker function for orthogonality of creating coordinate system. ```
``` e7393d4 ```
``` Add tests. ```
``` 6896c2b ```
``` Merge branch 'check_if_orthogonal' of https://github.com/szymag/sympy … ```
`…into check_if_orthogonal`
``` cf732b7 ```

### Upabjojr reviewed Jul 5, 2017

 v2 = Matrix([diff(eq[0], self.y), diff(eq[1], self.y), diff(eq[2], self.y)]) v3 = Matrix([diff(eq[0], self.z), diff(eq[1], self.z), diff(eq[2], self.z)]) if any(simplify(i[0]+i[1]+i[2]) == 0 for i in (v1, v2, v3)):

#### Upabjojr Jul 5, 2017

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This condition is technically the condition of non-degenerancy, it is not related to the orthogonality.

#### szymag Jul 5, 2017

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Yes, but we need to check that. `Dot` product with degenerated vector gives `0` and we get information that system is orthogonal but it isn't true.

### Upabjojr merged commit `8f3ceee` into sympy:master Jul 5, 2017 1 check passed

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