cho tam giac ABC, D. E lan luot la td cua AB, AC , BE X CD tai O . Keo dai AO X BC tai P . DE X AP tai I. SO sanh AI va IP. BP va PC
Sao ban hoi soay the cau nay lop 7 thi ok luon
Vi no wa hien nhien
Tui giai theo cach tinh dien tich
Chac ban da hoc vi lop 3 da hoc rui
1.chung minh PB=PC
Vi D la trung diem AB
Len dien tich ACD =dt CBD
“vi cung cung duong cao va day bang nhau”
Va dt OAD=dt OBD
Tru 2 dien tich cho nhau ta duoc
dt OAC=dt OBC (*)
tuong tu vi E la trung diem AC
len dt ABE=dt BCE va dt AOE=dt COE
tru cho nhau ta duoc:
dt OAB=dt OBC(**)
tu (*)(**) suy ra dt OAB=dt OAC
2 tam giac nay co cach AO chung
Len 2 duong cao ke tu B,C xuong AP phai bang nhau
Len xet tam giac OBP va tam giac OCP co
Chung canh OP va 2 duong cao xuong canh nay bang nhau “cmt”
Len dt OBP=dt OCP ma hai tam giac nay co chung duong cao
Ke tu O len 2 canh day tuong ung phai bang nhau
Tuc la PB=PC
Cau tiep theo ban cung lam tuong tu
Nho su dung ct tinh dien tich nhung nho su dung
Ket wa PB=PC
lop nam j ky vay
AI = IP
BP = PC
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Sao ban hoi soay the cau nay lop 7 thi ok luon
Vi no wa hien nhien
Tui giai theo cach tinh dien tich
Chac ban da hoc vi lop 3 da hoc rui
1.chung minh PB=PC
Vi D la trung diem AB
Len dien tich ACD =dt CBD
“vi cung cung duong cao va day bang nhau”
Va dt OAD=dt OBD
Tru 2 dien tich cho nhau ta duoc
dt OAC=dt OBC (*)
tuong tu vi E la trung diem AC
len dt ABE=dt BCE va dt AOE=dt COE
tru cho nhau ta duoc:
dt OAB=dt OBC(**)
tu (*)(**) suy ra dt OAB=dt OAC
2 tam giac nay co cach AO chung
Len 2 duong cao ke tu B,C xuong AP phai bang nhau
Len xet tam giac OBP va tam giac OCP co
Chung canh OP va 2 duong cao xuong canh nay bang nhau “cmt”
Len dt OBP=dt OCP ma hai tam giac nay co chung duong cao
Ke tu O len 2 canh day tuong ung phai bang nhau
Tuc la PB=PC
Cau tiep theo ban cung lam tuong tu
Nho su dung ct tinh dien tich nhung nho su dung
Ket wa PB=PC
lop nam j ky vay
AI = IP
BP = PC