Răspuns:
d) 96 cm2
Explicație pas cu pas:
OB/OA=3/4 <=> 4OB=3OA <=> OB=3OA/4
[tex] {ab}^{2} = {ob}^{2} + {ao}^{2} = ( { \frac{3ao}{4}) }^{2} + {ao}^{2} = \frac{9 {ao}^{2} }{16} + {ao}^{2} = \frac{9 {ao}^{2} + 16 {ao}^{2} }{16} = \frac{25 {ao}^{2} }{16} \\ ab = \frac{5ao}{4} [/tex]
P=4AB=4×5AO/4=5AO
P=5AO <=> 5AO=40 <=> AO=8 cm
AC=2AO=2×8=16 cm
P=4AB <=> 4AB=40 <=> AB=10 cm
[tex] {bo}^{2} = {ab}^{2} - {ao}^{2} = {10}^{2} - {8}^{2} = 100 - 64 = 36 \\ bo = \sqrt{36} = 6 \: cm[/tex]
BD=2BO=2×6=12 cm
Aria = AC×BD/2=16×12/2=8×12=96 cm2