# arcsin() return value with tiny imaginary part ?

Hi

where does this imaginary small quantity come from ?

SageMath notebook 9.1 W10

```
show(arcsin(sqrt(2)*sqrt(1/2)).n())
show(arcsin(sqrt(2)*sqrt(2^(-1))).n())
show(arcsin(sqrt(2)/sqrt(2)).n(),"\t ok no small imaginary part")
```