how do you use the verb "تحقیق کردن
how do you use the verb "تحقیق کردن"?when you want to say study/investstigate something, do you need to use "prep" with it ?
here is a sentence:
در اوضاع ستارگان و ماه و خورشید تحقیق می کنند
does it mean you need to put "dar" before the "sth" ?