xet tam giac abc co goc bac=90 do
\(\Rightarrow\)bc2=ab2+ac2(dinh li pytago)
\(\Rightarrow\)bc2=122+162=144+256=400
\(\Rightarrow\)bc=20 cm
co bd la phan giac goc bac(gia thiet)
\(\Rightarrow\)\(\frac{ad}{dc}\)=\(\frac{ab}{bc}\)(dinh li)
\(\Rightarrow\)\(\frac{ad}{ad+dc}\)=\(\frac{ab}{ab+bc}\)(tinh chat ti le thuc)
\(\Rightarrow\)\(\frac{ad}{ac}\)=\(\frac{ab}{ab+bc}\)(d thuoc ac)
\(\Rightarrow\)\(\frac{ad}{16}\)=\(\frac{12}{12+20}\)
\(\Rightarrow\)ad=\(\frac{12\cdot16}{32}\)=6 cm
co dc=ac-ad(d thuoc ac)
\(\Rightarrow\)dc=16-6=10 cm
b)xet tam giac bih va tam giac bda co
goc ibh=goc dba (vi bd la phan giac)
goc bhi =goc bad =90 do
\(\Rightarrow\)tam giac bih \(\sim\)tam giac bda (gg)
chung minh tuong tu tam giac abd \(\sim\)tam giac hbi
\(\Rightarrow\)goc adb =goc bih
ma goc bih = goc aid(doi dinh)
\(\Rightarrow\)goc adb = goc aid
\(\Rightarrow\)tam giac aid can
\(\Rightarrow\)ai=ad
xin loi mk k bt lam cau c
chuc ban hoc tot