So I (incited by some others) calculated the following

```
setprecision(15*10^5)
x=big(9528)/10000;
y=cos(x);
ys=string(y);
ys[306890:306931]
"459423813195289597370437889596885962619893..."
```

Now this is somehow wrong…The correct sequence is:

“459423813195289597370437889596885917728725…”

In fact doing one newton-iteration with the first wrong number:

```
yn=y;
yn=yn+(acos(yn)-x)*sqrt(1-yn^2);
```

gives the desired result above, which I would have assumed however to be correct in the first place…

So what is going wrong here?