Question

ΔABC cân tại A. Kẻ BH⊥AC ( H ∈ AC ). Tính BC nếu:

a)AH = 3 cm, HC = 2 cm

b)AH = 2 cm, HC = 1 cm

c)AH = 7,5 cm, HC = 1 cm

Answer 1

a: AB=AH+HC=5cm

=>BH=4cm

\(BC=\sqrt{4^2+2^2}=2\sqrt{5}\left(cm\right)\)

b: AB=AH+HC=3cm

\(BH=\sqrt{3^2-2^2}=\sqrt{5}\left(cm\right)\)

\(BC=\sqrt{5+1}=\sqrt{6}\left(cm\right)\)

c: AB=AH+HC=8,5cm

\(BH=\sqrt{8.5^2-7.5^2}=4\left(cm\right)\)

\(BC=\sqrt{4^2+1^2}=\sqrt{17}\left(cm\right)\)