a) AB = 10 cm si BC 9 cm ⇒ A = AB × BC = 10 × 9 = 90 cm²
b) [tex]BC = 2 \sqrt{3} ~cm~~si~~CD=3\sqrt{3}~cm ~\Rightarrow ~A = 2\times 3 \times (\sqrt{3})^2 = 18 cm^2[/tex]
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
