Array ( [0] => Array ( [title] => L15A [link] => https://www.youtube.com/embed/YBnFnW3CyJE ) [1] => Array ( [title] => L15B [link] => https://www.youtube.com/embed/V1tD1FnZ3gg ) [2] => Array ( [title] => L15C [link] => https://www.youtube.com/embed/gl6FgQROjXA ) ) 國立清華大學開放式課程OpenCourseWare(NTHU, OCW) - 第15R講 The First Fundamental Form and the Area of a Surface