View Compilation Error

0_0_35028467_8234.cpp: In function 'int main()':
0_0_35028467_8234.cpp:9:61: error: 'sqrt' was not declared in this scope
         printf("%.2f\n",sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));
                                                             ^