Proposed resolution:

In [complex.syn] change:

   template<class T> complex<T> polar(const T&, const T&);

to:

   template<class T> complex<T> polar(const T& rho, const T& theta = 0); 

In [complex.syn] polar is declared as follows:

   template<class T> complex<T> polar(const T&, const T&); 

In [complex.value.ops] it is declared as follows:

   template<class T> complex<T> polar(const T& rho, const T& theta = 0); 

Thus whether the second parameter is optional is not clear.