Error, (in evalf/RootOf) there are ambiguous values encoded in RootOf(_Z^2-2, 0) - Maple Help
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Error, (in evalf/RootOf) there are ambiguous values encoded in RootOf(...)

Error, (in convert/RootOf) there is ambiguity in RootOf(...)

 

Description

Examples

Description

The error occurs when evalf or convert are passed expressions that have ambiguity in regards to specification of roots.

Examples

Example 1

The numerical approximation of 12 used as a root selector is not helpful in distinguishing between the two roots, 1252, 12+52,  since both roots are a distance of exactly 52 from 12.

eRootOfx2x1,12

e:=RootOf_Z2_Z1,12

(2.1)

evalfe

Error, (in evalf/RootOf) there are ambiguous values encoded in RootOf(_Z^2-_Z-1, 1/2)

 

Solution

Use a different value as the root selector:

 

 eRootOfx2x1,32

eRootOf_Z2_Z1,32

(2.2)

 evalfe

1.618033989

(2.3)

 

Example 2

 

r1RootOf_Z22,0

r1:=RootOf_Z22,0

(2.4)

r2RootOf_Z22,index=1

r2:=RootOf_Z22,index=1

(2.5)

The numeric selector, 0, is not sufficient to distinguish whether r1 is the positive or negative root. Therefore, the following gcd computation is ambiguous: if r1 represents the positive root, then the GCD is x2, but if r1 represents the negative root, then the GCD is 1. Hence an error is raised:

gcdxr1,xr2;

Error, (in evalf/RootOf) there are ambiguous values encoded in RootOf(_Z^2-2, 0)

 

Solution

If you use a different selector that is not ambiguous, you can get an answer. Here, we use index=1 and index=2.

 

 r1RootOf_Z22,index=1

r1RootOf_Z22,index=1

(2.6)

 r2RootOf_Z22,index=2

r2RootOf_Z22,index=2

(2.7)

 gcdxr1,xr2;

1

(2.8)

We've specified two distinct roots, and their gcd is  1.

 

Example 3

convertRootOfx2x1,12,RootOf,form=index

Error, (in convert/RootOf) there is ambiguity in RootOf(_Z^2-_Z-1, 1/2)

 

Solution

This is the same root selector problem as in example 1.  As was done for that example, by choosing a different numeric selector for the RootOf, the specification is no longer ambiguous:

 convertRootOfx2x1,32,RootOf,form=index

RootOf_Z2_Z1,index=1

(2.9)

See Also

examples,RootOf

RootOf