360°÷13≈28°
360°÷13
=(351°+9°)÷13
=[351°+(9×60)′ ]÷13
=(351°+540′)÷13
=351°÷13+540′÷13
≈27°+42′
≈27°42′
答：将一周角13等分后,精确到度,每一个角大约是28°；精确到分,每一个角大约是27°42′