Question

ABC triunghi
BC=3 cm
AC=5 cm
unghiul C=120°
Aflati AB

Answer 1

Poti afla prin Pitagora. AB patrat+AC patrat=BC patrat=>AB patrat+25=9=>radical din AB=9-25=-16=> AB=4 cm

Answer 2

Am,construit,triunghiul,ABC,cu,baza,BC,pe,orizontala.Am,coborat,inaltimea,AD
perpendiculara,pe,prelungirea,BC.
In,ΔADC,dr,avem,m(∡ACD)=180°-120°(ip.)=60°=>m(∡CAD)=30°
=>CD-cateta,opusa,unghiului,de,30°,este,jumatate,din,ipotenuza
=>CD=AC/2=5/2cm=>BD=3+5/2=11/2cm
Cu,t.Pit.in,ΔADC,dr.,aflam,cateta,AD
AD²=AC²-CD²
AD²=25-25/4
AD²=75/4
AD=5√3/2
Tot,cu,t.Pit,in,ΔADB,dr.,aflam,ipotenuza,AB
AB²=AD²+BD²
AB²=75/4+121/4
AB²=196/4
AB=14/4=7/2cm