## Can't understand the meaning of some symbols

1. The problem statement, all variables and given/known data
This is an extract from elements of mechanics by giovanni.
I'[m unable to understand the meaning of $$R^d$$ and $$C^\infty$$

http://flic.kr/p/9K8P7p

2. Relevant equations

3. The attempt at a solution
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 Blog Entries: 27 Recognitions: Gold Member Homework Help Science Advisor hi shakgoku! Rd is the same as Rn … i assume "d" stands for "dimension" and C∞ is the space of functions which are differentiable "infinitely many" times
 Hey tiny-tim! Thank you , now everything in the page makes sense to me! :)