Decades: 1210s 1220s 1230s 1240s 1250s - 1260s - 1270s 1280s 1290s 1300s 1310s
Years: 1256 1257 1258 1259 1260 - 1261 - 1262 1263 1264 1265 1266
Births
Deaths
... equation is now in a form in which we can conveniently complete the square[?]. To "complete the square" is to add a ...