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What do you eat for breakfast every morning?

Bài 5: Cho △DEF cân tại D có đường trung tuyến DI

a) C/m: △DEI = △DFI

b) C/m: DI ⊥ EF

c) Kẻ đường trung tuyến EN. C/m: IN // ED

Refer:

The gift Dad gave on his birthday was a beautiful fountain pen. Small round pen, pretty, as long as one glove of mine. Tapered pen cap bright orange. The pen's core is made of soft, flexible plastic and the spring makes it easy to pump daily ink. The smooth nib creates round, soft strokes. I love my pen very much, when I finish writing, I usually wipe it off with a soft rag, the pen cap carefully then put it in the pen box. Thanks to that, my pen is always new and durable. Dad's gift is so meaningful!

Xét △ ABD và △ ADC ta có:

AD chung

AB = AC(△ ABC cân tại A)

\(\widehat{BAD}\) = \(\widehat{DAC}\)(AD là phân giác của góc A)

→ △ ABD=△ ADC(c.g.c)

→ BD = DC(2 cặp cạnh tương ứng)

Vì BD = DC(cmt)

→ D là trung điểm của BC

= \(\dfrac{3}{2}\)x³y⁶z²

Refer:

My pet is a Vietnamese cat named Binko. He is an adorable black and white cat with a very adorable round face. Binko is always friendly to me, but wary of strangers. He loves many things such as lying on the carpet, lying under the sun, he also loves playing and especially eating.

Trong △ABC cân tại A ta có:

AD là tia phân giác của \(\widehat{BAC}\)

⇒ AD cũng là đường cao của △ ABC 

⇒ AD ⊥ BC

18. D

19. C