This group of functions is a part of the (famous) C standard library. A lot of functions of this group are inherited in C++. There are some differences between C and C++ in the use of complex numbers. C++ doesn't provide complex numbers handling from that library but from its own C++ standard library by using the class template
Almost all these functions are designed to work with and manipulate floating-point numbers. In standard C, this library is known as
math.h (a filename), which we mention in the header of a C program, so that we can use its functions.