View Compilation Error

0_0_27802974_27497.cpp: In function 'void Gauss(int)':
0_0_27802974_27497.cpp:31:21: error: 'fabs' was not declared in this scope
    if(fabs(A[k][col]) > fabs(A[row][col]))
                     ^
0_0_27802974_27497.cpp:34:20: error: 'fabs' was not declared in this scope
   if(fabs(A[r][col]) > eps)
                    ^