두 원의 공통 외접선 작도하기(Constructing two circles' outer tangents) : http://me2.do/x6sFqXHu YouTube : https://youtu.be/mz1WF3zZyL4 GeogebraTube : https://ggbm.at/eF9QHhr4 ggb problem : http://me2.do/Fec3MGnz[br][br]기하작도문제 : https://ggbm.at/jFazZw2g 수학자료실 강의실 : https://goo.gl/czyJLW YouTube Channel : https://goo.gl/JpzU5i twitter : https://twitter.com/mineungi [br]