Many thanks, Christian: that's the way…
I added a note in the wiki:
	http://wiki.contextgarden.net/Reference/en/placeformula

Best regards: OK
On 17 nov. 2011, at 14:48, Christian wrote:

>> Is it possible to reset the numbers which appear after invoking
>> \placeformula?
>> 
>> To be more precise, I mean the following situation:
>> 
>> \starttext
>> 
>> Euler says
>> 	\placeformula
>> 	\startformula
>> 		{\rm e}^{{\rm i} \pi} + 1 = 0.
>> 	\stopformula
>> The above formula will have number (1). Euler's formula is the same as the
>> following
>> 	\placeformula
>> 	\startformula
>> 		{\rm e}^{{\rm i} \pi} = - 1.
>> 	\stopformula
>> The above formula will have number (2), but for some reasons I wish to
>> number it again as (1).
>> \stoptext
>> 
>> I would like to have a solution which works with ConTeXt mkiv.
>> 
>> Thanks for any advice, and best regards: OK
> 
> \resetnumber[formula]
> or
> \setnumber[formula]{<insert number>}
> 
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