Question

calculati aria dreptunghiului abcd stiind ca
a) ab=10 cm si bc=9cm
b) bc= 2radical 3 cm si cd=3radical3 cm
c) Aabc =15 cm2
d) Acod = 9 cm2 ,unde ac > bd = (0)

Answer 1

a)  AB = 10 cm si BC 9 cm  ⇒ A = AB × BC = 10 × 9 = 90 cm²

b)  $BC = 2 \sqrt{3} ~cm~~si~~CD=3\sqrt{3}~cm ~\Rightarrow ~A = 2\times 3 \times (\sqrt{3})^2 = 18 cm^2$

c) AriaΔABC = 15 cm²  ⇒ A = 2 × AriaΔABC = 2 × 15 = 30 cm²

d)  Aria ΔCOD = 9cm², unde {O} = AC ∩ BD  
⇒ A = 4 × AriaΔCOD =  4 × 9 = 36 cm²