View Compilation Error

0_0_6376662_23122.cpp: In function `double dist(fish, fish)':
0_0_6376662_23122.cpp:11: error: `sqrt' undeclared (first use this function)
0_0_6376662_23122.cpp:11: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6376662_23122.cpp: In function `fish center1(fish, fish)':
0_0_6376662_23122.cpp:21: error: `sqrt' undeclared (first use this function)
0_0_6376662_23122.cpp:22: error: `fabs' undeclared (first use this function)
0_0_6376662_23122.cpp:30: error: `atan' undeclared (first use this function)
0_0_6376662_23122.cpp:31: error: `cos' undeclared (first use this function)
0_0_6376662_23122.cpp:32: error: `sin' undeclared (first use this function)