4.
a)180°-90°-30°=60°
b)AC=BC/2 (teorema ∡30°) =>AC=5 cm
c)AB²+AC²=BC² (t.Pit.) =>AB²=100-25=75 =>AB=5√3 cm
5.
a)DAC=180°-60°-50°=70°
ACD=CAB (unghiuri formate de o secanta, AC si doua drepte paralele)
=>DAB=70°+50°=120°
b)BAC=50° (am explicat de ce la punctul a)
c)DAB=BCD (definitia paralelogram)
ACB=DAC=70°
