Name: Aliaksandr Dubrouski Date: 09/14/15-10:46:37 AM Z


@Sun Qingfeng

Looks like complex root of (x-1). Could you please try setting assumptions
for x to be Real and see the result? My guess is that Calc uses Simplify
internally and assumptions are resolved by the type of argument,
assumptions starting from Complex as the most general class.

2015-09-13 9:41 GMT+03:00 Sun Qingfeng <[noreply_at_HIDDEN-E-MAIL]>:

> Several Months ago, I find a problem in the “Calc” function.
>
> Now, In the new version of FC9.0 with mathematica 10.1, a similar problem
> appears again:
>
> $Assumptions = {x > 1}
>
> Sqrt[x - 1] // Calc
>
> and the output looks like:
>
> I Sqrt[1-x] exp(I \[Pi] \[LeftFloor]-(arg(1-x)/(2 \[Pi]))\[RightFloor]+9 I
> \[Pi] \[LeftFloor]1/2-arg(1-x)/(2 \[Pi])\[RightFloor])
>
> But I think the expected output should be:
> Sqrt[x - 1]
>
>

-- 
Regards,
            Aliaksandr Dubrouski