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**Halliday and Resnick**and it says that

Code:

```
The meter is the length of the path traveled by light in a vacuum
during a time interval of 1/299 792 458 of a second.
This time interval was chosen so that the speed of light c is exactly
c = 299 792 458 m/s.
```

**dx formula**of motion (you get

**dx = 1m**)

but how did we calculate

**the speed of light in m/s very precisely**before redefining the meter? The calculation of the speed depends in the previous definition of the meter right? So how does this new definition of meter can use the speed of light which was calculated using another definition of the meter? It does not really make sense to me...