[Scilab-users] acos leads to complex values

[Stéphane Mottelet]

Le 29/01/2019 à 16:45, Carrico, Paul a écrit :
>
> Dear All
>
> I spent some time in looking for a mistake in my code ; finally I’ve 
> found that the ACOS of a real vector leads to some complex values (???)
>
> acos(Scar_P(:,1)./ CM_x_CN(:,1))

Are your really sure, because we may have

--> x=-1-%eps
  x  =

   -1.


--> acos(x)
  ans  =

    3.1415927 - 2.107D-08i

S.


> (the formula worked so far)
>
> I checked that the input values are correct:
>
> -Comprised between [-1; 1] using MIN and MAX
>
> -Composed only of real values using ISREAL (all the vectors are correct)
>
> Thus I do not understand why complex values appear ?
>
> May it come from the vectorization ?
>
> Paul
>
>
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-- 
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet

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