Question

em cần gấp mn giúp em 

Answer 1

a) Có \(BC=BH+CH=25\)

Áp dụng hệ thức trong tam giác vuông có:

\(AH^2=BH.CH=144\Rightarrow AH=12\)

\(AB^2=BH.BC=225\Rightarrow AB=15\)

\(AC^2=CH.BC=400\Rightarrow AC=20\)

\(sinB=\dfrac{AC}{BC}=\dfrac{20}{25}\Rightarrow\widehat{B}\approx53^0\)

\(sinC=\dfrac{AB}{BC}=\dfrac{15}{25}\Rightarrow\widehat{C}\approx37^0\)

b) Có \(\dfrac{sinB}{sinC}=\dfrac{AC}{BC}:\dfrac{AB}{BC}=\dfrac{AC}{AB}\)