1 | initial version |

The issue arises because the transition map from chart `Y`

to chart `X_U`

has not been defined. You must implement it as follows, just after the definition of `transit_Y_to_X`

:

```
transit_Y_to_X.set_inverse(t, atan2(y, x) - Omega*t, atan2(z, sqrt(x^2+y^2)), sqrt(x^2+y^2+z^2),
verbose=True)
transit_Y_to_X.inverse().display()
```

Then the display of the connection coefficients w.r.t. `Y.frame()`

is OK (albeit quite slow: while investing your issue, I've discovered that the computation efficiency can be significantly improved; I'll open a ticket for this).

2 | No.2 Revision |

The issue arises because the transition map from chart `Y`

to chart `X_U`

has not been defined. You must implement it as follows, just after the definition of `transit_Y_to_X`

:

```
transit_Y_to_X.set_inverse(t, atan2(y, x) - Omega*t, atan2(z, sqrt(x^2+y^2)), sqrt(x^2+y^2+z^2),
verbose=True)
transit_Y_to_X.inverse().display()
```

Then the display of the connection coefficients w.r.t. `Y.frame()`

~~is OK (albeit ~~works, albeit quite ~~slow: ~~slow (*).

(*) while investing your issue, I've discovered that the computation ~~efficiency ~~can be significantly ~~improved; I'll open a ticket for this).~~improved by reordering some loops; this is now Trac #28543.

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