21:54:00 04/08/2011
Ai có bài hhkg hay thì post lên nha.
09:56:00 06/08/2011
tu djen s.abc co sa=sb=sc=1,Ssab=Ssac=Ssbc va 2mp (sab),(abc) vuog goc voi nhau.tinh bkinh mat cau noi tip tu dien s.abc
11:04:00 07/08/2011
Bai ni de sai. Hi. Tu 2 du kien dau tien =>tu dien nay deu. =>ko the co (sab)v(abc)
10:41:00 08/08/2011
k sai mu.dug do
12:20:00 13/08/2011
Trog kg oxyz cho hjh lap fuog ABCD.ABCD,A(0,0,0)B(1,0,0) D(0,1,0)A(0,0,1)Vjet ptmp chua ACtao vs oxy 1goc ¤ bjt cos¤=1/can6
23:41:00 13/08/2011
Cho tu djen ABCD co AB=CD,AC=BD,AD=BC,va (cab)vuog(dab).cmr. Cot<BCD nkan cot<BDC =1/2