If the "fuzz" on some pterodactyls is indeed confirmed to be feathers, the originof feathers can be traced back to more ancient times.
如果某些翼手龙身上的“绒毛”被证实的确为羽毛的话，那羽毛的起源就可以上溯到更为远古的年代。
2
Wiktionary tells us that the originof the expression "no strings attached" may date back to ancient times.
维基词典指出，“无附加条件”这一说法的起源可以追溯到古代。
3
So, switching the area, moving the area to the other side, I'll get double integral of xdA is the area oforigintimes the x coordinate of the center of mass.