C++ 程序中的 #include cmath 与 #include math.h [重复]

#include <cmath> 与 #include <math.h>

cpp
#include 
#include 
int main() {
    double x = 16.0;
    double result = std::sqrt(x);
    std::cout << "The square root of " << x << " is " << result << std::endl;
    return 0;
}

cpp
#include 
#include 
int main() {
    double x = -5.6;
    double result = std::abs(x);
    std::cout << "The absolute value of " << x << " is " << result << std::endl;
    return 0;
}