This is the 121st most frequent Indonesian word.
diketahui
"Known" or "understood."
'Diketahui' is used here to indicate that the subject (the cause) is not yet known or identified.
Penyebab dari masalah tersebut belum diketahui.
The cause of the problem is not yet known.
In this context, 'diketahui' is used to imply that the subject (the additional information) can be ascertained or learned through an action (research).
Informasi tambahan tersebut dapat diketahui melalui penelitian lebih lanjut.
The additional information can be known through further research.
Here, 'diketahui' conveys that the subject (the number of students) has been determined or recognized by the teacher.