This is only just one of the reasons why I've given up on "realpart(z)" and use
(z+conjugate(z))/2
instead.
At 09:09 AM 12/13/2012, Stavros Macrakis wrote:
>Currently,
>
> realpart(sqrt(a)) =>
> cos(atan2(0,a)/2)*sqrt(abs(a))
>
>This is of course correct, but not very useful.
>
>For one thing, it gives an error for a=0.
>For another, it doesn't simplify to sqrt(-a) with assume(a<=0). (Though it does simplify to sqrt(a) for a>=0.)
>
>Is there some way to force realpart to use asksign in cases like this? I seem to remember that that was always what it did, but I couldn't find a discussion of a change in my mail archives.
>
>As we improve support for conditionals, another useful value would be (if a>0 then sqrt(a) else 0) -- or maybe (if a>=0 then sqrt(a) else 0). But again, currently we have the problem that the simplifier doesn't do a very good job on expressions like this.
>
> -s