ban tu ve hinh nha
ta co \(\frac{AB}{AC}=\frac{3}{4}\Rightarrow\frac{AB}{3}=\frac{AC}{4}=\frac{AB+AC}{3+4}=\frac{21}{7}=3\)
\(\Rightarrow AB=9,AC=12\)
ap dung dl pitago vao tam giac ABC vuong tai A
\(AB^2+AC^2=BC^2\Rightarrow BC=15\)
B. ap dung he thuc luong trong tam gia vuong ABC co
\(AH\cdot BC=AC\cdot AB\Rightarrow AH=\frac{12\cdot9}{15}=7,2\)
\(AB^2=BH\cdot CB\Rightarrow BH=\frac{9^2}{15}=5.4\)\(\Rightarrow CH=BC-BH=15-5,4=9.6\)