问计算出的C/C++ log10函数产生的值不正确

EN

#include <math.h>
#include <iostream>

int main()
{
   double a = log10(1/200);
   double b = log10(0.005);

   std::cout << "The value of a is " << a << " and b is " << b << std::endl;
}

g++ -o math math.cpp
./math

The value of a is -inf and b is -2.30103

#include <math.h>
#include <stdio.h>

int main()
{
   double a = log10(1/200);
   double b = log10(0.005);

   printf("The value of a is %f and b is %f\n", a, b);
}

gcc -o math math.c -lm
./math

The value of a is -inf and b is -2.301030