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[MUG] Re: Inplicitplot3d problem
| [MUG] Re: Inplicitplot3d problem |
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Author: Robert Israel
Posted: 16/01/2001 18:18:43 GMT
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>> From: Robert Israel
The question is, what do you mean by a non-integer power of an expression
when that expression happens to be negative? In your example, you have
(expression)^(1/.6), which becomes (expression)^1.666666667. Now you
don't really want the float 1.666666667, but instead the rational 5/3,
and moreover you want the real version of the 5/3 power to be used rather
than the principal branch, which is complex. Maple provides "surd" for
this purpose. For convenience, you might look at "&^" in my Maple Advisor
Database, http://www.math.ubc.ca/~israel/advisor, which provides
"elementary" fractional powers. For example, you could say:
> G:= (((((x/90)*(1+((z*(-0.3))/250)))&^(2/1.0)+(
> (y/90)*(1+((z*(-0.3))/250)))&^(2/1.0))&^(1.0/0.6)+(z/250)&^
> (2/0.6))&^0.6)-1=0;
and I think implicitplot3d will display this satisfactorily.
Robert Israel
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia
Vancouver, BC, Canada V6T 1Z2
On Tue, 9 Jan 2001, Elodie Calais wrote:
> I would like to use the maple implicitplot3d function in order to
> display tapered superquadric curves.
> Unfortunately, as this equation contains real exponents, maple only
> displays half of the surface ; but, if I change the real exponent in a
> integer one, maple is able to display the whole surface.
> I would like to know why I have this problem and also how I should solve
> it.
> Here are the 2 implicit functions I have tried to display :
> - with real exponents
> f(x,y,z)=(((((x/90)*(1+((z*(-0.3))/250)))^(2/1.0)+(
> (y/90)*(1+((z*(-0.3))/250)))^(2/1.0))^(1.0/0.6)+(z/250)^
> (2/0.6))^0.6)-1=0
>
> - with integer exponents
> f(x,y,z)=(((((x/90)*(1+((z*(-0.3))/250)))^(2/1.0)+(
> (y/90)*(1+((z*(-0.3))/250)))^(2/1.0))^(1.0/0.5)+(z/250)^
> (2/0.5))^0.5)-1=0
>
> Thank you very much for your precious help.
> Sincerely yours
>
> Elodie CALAIS |
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