Differentiation doesn't work

[theasder]

Enjoy! -> d/dx(cos(x))
I'm so sorry, something wrong. Please feel free to report this. [DEBUG CODE30]

========== DEBUG INFO ==========
str:       d/dx(cos(x))

scan_rslt: 
@lexeds:   [{:token=>:UNKNOW, :value=>"d/dx", :els=>[]}]

[jackmaney]

You need to enter the command postulate zfc_analysis to do almost anything useful. No, this shouldn't be necessary.

Hi guys,thank you for using Hilbert.
You need to execute "postulate zfc_analysis" if you wanna do real analysis.

Enjoy! -> postulate zfc_analysis
success! :)
Enjoy! -> d/dx(cos(x))
- sin( x )
Enjoy! ->