View Compilation Error

0_0_10307042_32715.cpp: In function `std::vector<xy, std::allocator<xy> > read_and_norm()':
0_0_10307042_32715.cpp:73: error: `sqrt' undeclared (first use this function)
0_0_10307042_32715.cpp:73: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10307042_32715.cpp: In function `bool close(const xy&, const xy&)':
0_0_10307042_32715.cpp:92: error: `fabs' undeclared (first use this function)