Question

Fie triunghiul ABC isioscel, AB=AC si masura unghiului BAc =30 grade .Daca AB=40 cm BD_|_Ac , D apartine Ac , calculati BD

Answer 1

Scriem aria ΔABC in 2 feluri :
A=AC·BD/2
A=1/2·AB·AC·sin<A
Atunci: AC·BD=AB²sin30⇒BD=(AB²sin30)/AC=(AB·AB·sin30)/AB=
=AB·sin30=40·1/2=20
BD=20
Obs. AB=AC(ΔABC-isoscel)