The contents and meaning of the header <cmath>
are the same as the C standard library header <math.h>,
with the addition of
a three-dimensional hypotenuse function and
the mathematical special functions described in [sf.cmath].
If any argument of arithmetic type
corresponding to a double parameter
has type longdouble,
then all arguments of arithmetic type
corresponding to double parameters
are effectively cast to longdouble.
Otherwise, if any argument of arithmetic type
corresponding to a double parameter
has type double
or an integer type,
then all arguments of arithmetic type
corresponding to double parameters
are effectively cast to double.