타원에서의 빛 반사(Reflection of Light on a Ellipse) : https://goo.gl/eQG9hs gif : https://goo.gl/NDfb31 YouTube : https://youtu.be/Ahi2XZBSY7A[br][br]수학자료실 강의실 : https://goo.gl/czyJLW   YouTube Channel : https://goo.gl/JpzU5i twitter :  https://twitter.com/mineungi