Xét \(\Delta ABC\) vuông tại A có :

\(BC^2=AC^2+AB^2\)(Theo định lý Pi-ta-go)

\(\Leftrightarrow\)\(BC^2=12^2+5^2\)

\(\Leftrightarrow\)\(BC=13cm\)

Xét \(\Delta ABC\) có phân giác BK

=> \(\dfrac{AK}{AB}=\dfrac{KC}{BC}\)

\(\Leftrightarrow\) \(\dfrac{AK}{5}=\dfrac{KC}{13}\)

Mà \(AK+KC=AC=12cm\)

Áp dung t/c dãy tỉ số bằng nhau ta có:

\(\dfrac{AK}{5}=\dfrac{KC}{13}=\dfrac{AK+KC}{18}=\dfrac{12}{18}=\dfrac{2}{3}\)

=> \(\left\{{}\begin{matrix}AK=\dfrac{10}{3}cm\\CK=\dfrac{26}{3}cm\end{matrix}\right.\)

Vậy...

Put the corect in the brackets in the past simple or past perfect :

1 - After taking a bath, he (go).................. to bed

2 - What (be)............ he when he (be).............. young?

3 - Our teacher (tell)............... us yesterday that he (visit).............. England in 1970

HELP ME, PLEASE