Question

Answer 1

lx

Answer 2

lỗi

Answer 3

1,

Ta có :

AD là tia phân giác \(\widehat{BAC}\)

=> \(\dfrac{AB}{AC}=\dfrac{BD}{CD}\)

=> \(\dfrac{5}{8,5}=\dfrac{3}{CD}\)

=> \(CD=\dfrac{3.8,5}{5}=5,1\left(cm\right)\)

 

Answer 4

a) △ABD và △BDC có: \(\dfrac{AB}{BD}=\dfrac{BD}{DC}=\dfrac{AD}{BC}\left(=\dfrac{1}{2}\right)\)

\(\Rightarrow\)△ABD∼△BDC (c-c-c).

b) △ABD∼△BDC \(\Rightarrow\widehat{ABD}=\widehat{BDC}\)

\(\Rightarrow\)AB//CD \(\Rightarrow\)ABCD là hình thang.

Answer 5

mờ quá