In ∆ ABC dr =>Tin
AD²=BD×DC
DC =12²:9
DC= 144:9
DC=16
BC = DC+BD= 9+16= 25
In ∆ ABC dr => T cat
AB²= BD×BC
AB² =9×25
AB² =225
AB=√225
AB=15 cm
In ∆ ABC dr =>TP
AB² +AC² =BC²
15²+AC² =25²
AC² =625-225
AC=√400
AC=20 cm
sun B =AC/BC
sin B = 20/25
sin B = 4/5
coa B = AB/BC
cos B= 15/25
cos B =3/5
tgC =AB/AC
tg C =15/20
tg C = 3/4
ctg C=AC/AB
ctg C=20/15
ctgC=4/3
