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Dear GAP-Forum,

since we are very unexperienced in the use of GAP we would

like to know how to deal with the following problem:We are given a finitly presented group G (we know how to encode

this in GAP) and want GAP to replace each generator by a product

of two new symbols (a representation of G) thus giving us a

new set of relators. Then we would like GAP to give us the

Fox-derivatives of this set of new relators.Making a trivial example:

replace: a -> xv, b -> wy Relator: r= a^-1 b a^3 -> v^-1 x^-1 w y (x v)^3 partial Fox-derivative for x: -> -v^-1 + v^-1 x^-1 w y (1+v+v^2)Where in the manual shall we turn pages to find how to do this?

Best regards,

Stephan Rosebrock and Cynthia Hog-Angeloni

Irina Kholodna has written a short GAP package for computing a minimal set of

generators for the second homotopy group of the CW-space associated to a finite

presentation of a (finite) group. The package, which includes a function for

computing Fox derivatives, is included as an appendix to a paper in the

Journal of Mathematics and Computation (1999, http://www.lms.ac.uk). The

package is also available from http://hamilton.nuigalway.ie.

Best regards,

Graham Ellis

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