View Compilation Error

332252_0_28284.cpp: In function `double dis(Point, Point)':
332252_0_28284.cpp:12: error: `sqrt' undeclared (first use this function)
332252_0_28284.cpp:12: error: (Each undeclared identifier is reported only once for each function it appears in.)
332252_0_28284.cpp: In function `int main()':
332252_0_28284.cpp:45: error: `qsort' undeclared (first use this function)