[isabelle] general commands for rewritting real expressions

Hi everybody.

Whenever I have a rewriting problem (usually involving real expressions) I
try first few general commands like
    by auto
    by simp
    by (simp add: field_simps)
    by sledgehammer

Sometimes none work, for example for
    lemma "(x::real)>0 ==>
                   ((1+x)*(1+x)*(1+x) powr (1/3))

In such cases I sometimes decompose the problem to a few simpler ones, and
sometimes delve into the HOL libraries looking for something useful to add
to simp, possibly reversed.

Since these solutions are somewhat tedious, my question is - are there
other general commands I can try at this point? Or maybe something like
'field_simps' that is more appropriate for real expressions? Any advice
would be appreciated.


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