Apparently I have at some point made so that y''=xSin[y], and it seem like I can't clear it in any way. I can't do Clear[y''] and I tried to do ClearAll["Global‘"], but it didn't effect y'', so some help here would be appreciated.
You can try y'' =. (i.e., Unset[y'']) or Remove[y].
y'' =.
Unset[y'']
Remove[y]
It worked. Thanks a bunch.
