View Compilation Error

0_0_38332456_15907.cpp: In function 'int main()':
0_0_38332456_15907.cpp:6:15: error: 'fabs' was not declared in this scope
     x=fabs(c-a);
               ^
0_0_38332456_15907.cpp:8:19: error: 'sqrt' was not declared in this scope
     x=sqrt(x*x+y*y);
                   ^