Răspuns:
ΔMAD este dreptunghic in ∠ MAD si m(∠ ADM)= 30° => AM = [tex]\frac{MD}{2}[/tex]
AM^2 + AD^2 = MD^2
<=> AM^2 + AD^2 = (2AM)^2 = 4 AM^ 2 | - AM^2
<=> AD^2 = 3 AM^2 => 3 AM^ 2 = 12| : 3
=> AM^2 = 4 => AM= 2 cm
=> [tex]\frac{2}{BM}= \frac{4}{3}[/tex] => BM = 2*3/4 = 1,5
=> AB = 2+ 1,5 = 3,5 cm
=> A ΔADCB = 3,5* 12 = 42 [tex]cm^{2}[/tex]
A Δ AMD = AD* AM /2 = 12* 2 /2 =12 [tex]cm^{2}[/tex]
A MDCB = A ADCB - A Δ ADM = 42 [tex]cm^{2}[/tex] - 12 [tex]cm^{2}[/tex] = 30 [tex]cm^{2}[/tex]
