### Sage doesn't simplify a fraction if it's multiplied by 2

Hello, for some reason sage doesn't simplify a trigonometric expression:

```
sage: ( 2 * (1-cos(x)) / sqrt(1-cos(x)) ).simplify_full()
-2*(cos(x) - 1)/sqrt(-cos(x) + 1)
```

while I'd expect `sqrt(1-cos(x))`

.

I also tried a nice `simplify_chain_real`

function (thanks eric_g for the hint) but got the same result:

```
sage: from sage.manifolds.utilities import simplify_chain_real
sage: simplify_chain_real( 2 * (1-cos(x)) / sqrt(1-cos(x)) )
-2*(cos(x) - 1)/sqrt(-cos(x) + 1)
```

The weird thing is that it works without the `2*`

part:

```
sage: ( (1-cos(x)) / sqrt(1-cos(x)) ).simplify_full()
sqrt(-cos(x) + 1)
```

And even replacing `-`

with `+`

makes it working:

```
sage: ( 2*(1+cos(x))/sqrt(1+cos(x)) ).simplify_full()
2*sqrt(cos(x) + 1)
```

I mean, obviously, it can do that kind of simplification. But I can't make it simplify the `2*(1-cos(x))/sqrt(1-cos(x))`

expression. What do I miss?