Array ( [0] => Array ( [title] => L5A [link] => https://www.youtube.com/embed/hXiOMt-t27U ) [1] => Array ( [title] => L5B [link] => https://www.youtube.com/embed/zTrfCkXIOVA ) [2] => Array ( [title] => L5C [link] => https://www.youtube.com/embed/64CpssnO5lw ) [3] => Array ( [title] => L5D [link] => https://www.youtube.com/embed/5Y5nJWrLx2w ) ) 國立清華大學開放式課程OpenCourseWare(NTHU, OCW) - 第5R講 2.5 Closure of a set