Defined in header <ratio> template< class R1, class R2 >
using ratio_divide = /* see below */;
The alias template std::ratio_divide denotes the result of dividing two exact rational fractions represented by the std::ratio specializations R1 and R2.
The result is a std::ratio specialization std::ratio<U, V>, such that given Num == R1::num * R2::den and Denom == R1::den * R2::num (computed without arithmetic overflow), U is std::ratio<Num, Denom>::num and V