Îⁿ-chiu-kak

Wikipedia (chū-iû ê pek-kho-choân-su) beh kā lí kóng...

kí-hô-ha̍k tiong, îⁿ ê 2 tiâu koah-soàⁿ tī îⁿ-chiu téng sio-tú, chiū ē hêng-sêng chi̍t ê îⁿ-chiu-kak (圓周角).