View Compilation Error

0_0_38888479_11558.cpp: In function 'double dis(point, point)':
0_0_38888479_11558.cpp:18:16: error: 'sqrt' was not declared in this scope
   18 |         return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
      |                ^~~~
0_0_38888479_11558.cpp: In function 'double closest(int, int)':
0_0_38888479_11558.cpp:28:20: error: 'fabs' was not declared in this scope; did you mean 'labs'?
   28 |                 if(fabs(a[i].x-a[m].x)<d) b[++k]=a[i];//中线两侧距离d的所有点
      |                    ^~~~
      |                    labs