Salut !
a) figure 1 : a²
figure 2 : πx²
figure 3 : 10k
figure 4 : (3p × 3p) ÷ 2 = 9p²/2
b) a = 5 cm donc aire du carré = a² = 5² = 25 (cm)²
x=3 cm donc aire du disque = π×3² = 9π ≅ 28,3 (cm²)
k=3 cm donc, périmètre figure 3 = 10k = 10 × 3 = 30 (cm)
p=2 cm donc aire du triangle = 9p²/2 = (9×2²)/2 = 18 (cm²)
