where前面能用介词吗?请教两个英语句子,chinaisthebirthplaceofknites,fromwherekiteflyingspreadtoJapan；shestoodnearthewindow,fromwhereshesawthenationalflagbeingraised.我知道在定语从句中where就等于

　　where前面能用介词吗?

　　请教两个英语句子,chinaisthebirthplaceofknites,fromwherekiteflyingspreadtoJapan；shestoodnearthewindow,fromwhereshesawthenationalflagbeingraised.

　　我知道在定语从句中where就等于介词加which,where前面是不能有介词的,那么上面两个句字是什么从句呢?该如何分析呢?介词后面怎么加了where呀?