Function: poltschirnhaus
Section: number_fields
C-Name: tschirnhaus
Prototype: G
Help: poltschirnhaus(x): random Tschirnhausen transformation of the
 polynomial x.
Doc: applies a random Tschirnhausen
 transformation to the polynomial $x$, which is assumed to be non-constant
 and separable, so as to obtain a new equation for the \'etale algebra
 defined by $x$. This is for instance useful when computing resolvents,
 hence is used by the \kbd{polgalois} function.
