Question

[Phạm Phương Anh]

Cho tam giác ABC có AB=12cm, AC=15cm, BC=20cm. Trên Ac lấy M sao cho AM=5cm. Kẻ MN//BC( N thuộc AB), NQ// AC.

Tính AN, BQ.

Answer 1

[Trần Quân]

Vì MN//BC

=>\(\dfrac{AN}{AB}=\dfrac{AM}{AC}\)<=>\(\dfrac{AN}{12}=\dfrac{5}{15}\)<=>AN=\(\dfrac{5.12}{15}\)<=>AN=4 (cm)

Vì NQ//AC

=>\(\dfrac{QC}{BC}=\dfrac{NA}{AB}\)<=>\(\dfrac{QC}{20}=\dfrac{4}{12}\)<=>QC=\(\dfrac{4.20}{12}\)<=>QC=\(\dfrac{20}{3}\) (cm)

=>BQ = BC - QC =20 - \(\dfrac{20}{3}\)=\(\dfrac{40}{3}\)(cm)

chúc bạn học tốt!