Formula 1: (Se foloseste in tehnica)
A = π × D² / 4 = π × 10² / 4 = π × 100 / 4 = 25π cm²
Formula 2
A = π × R²
R = D/2 = 10/2 = 5 cm
A = π × R² = π × 5² = = 25π cm^2
