Eratosthenes of Cyrene ( Ancient Greek : Ἐρατοσθένης , IPA : ( eratostʰénɛːs ) ; English \ / ɛrəˈtɒsθəniːz \ / ; c. 276 BC - c. 195\/194 BC ) was a Greek mathematician , geographer , poet , astronomer , and music theorist .
Eratosthenes of Cyrene 276 BC-194 BC ) was a third century BC Greek mathematician , geographer and astronomer .