Question

[phi manh quang vinh]

cho tam giac abc co S = 156m2 E la diem chinh giua BC Tren doan AE lay diem  chinh la I noi Bi  keo daii cat o D tinh S aid

Answer 1

[vi vi vi]

tu ve hinh noi d voi e s tam giac ace = s tam giac aeb vi chieu cao ha tu dinh a xuong day la chieu cao chung . day ce = day eb e la chung diem cua cb s tam aeb hay ace la 156 :2 =78 cm vuong s tam giac ade =deb (1)vi chieu cao ha tu dinh d xuong day la chieu cao chung .day ce = day eb ,s tam giac aib =s tam giac ibe (2) vi chung chieu cao ha tu dinh b xuong day la chieu cao chung ma day ai =ie s tam giac adi = s tam giac die (3) vi chung chieu cao ha tu dinh d xuong day ma day ai =ie .tu (2) va (3 ) suy ra stam giac atb +s tgi aib =s tgi ibe +s tam giac die s tam giac adb = s tgi bds (4) tu (1) va (4) suy ra s tam giac dce= s tgi deb = s tgi adb .ma s tgi dce |+ s tgi =s tgi abc

s tgi abd =156 :3 =52 cm stg atb =1/2 s abe vi chieu cao ha tu dinh b xuong day la chung day ai =1/2 day ae s abe = 156 :2 =78 s aib =78 ;2 =39 s adi 52 - 39 =13