View Compilation Error

0_0_33877357_4818.cpp: In function 'int main()':
0_0_33877357_4818.cpp:50:74: error: 'sqr' was not declared in this scope
             double ans=sqr(dx+dy+sqrt(max(0.0,pow(dx-dy,2)+4*pow(cxy,2))));
                                                                          ^