BO₁=O₁D=BD·(1/2)BD₁=BO₁+O₁D₁=BO₁+O₁D/2=BD·(3/4) BO₂=O₂D₁=BD₁·(1/2)=BD·(3/4)·(1/2)BD₂=BO₂+O₂D₂=BO₂+O₂D₁/2=BD₁·(3/4)=BD·(3/4)² BO₃=O₃D₂=BD₂·(1/2)=BD·(3/4)²·(1/2)BD₃=BO₃+O₃D₃=BO₃+O₃D₃/2=BD₃·(3/4)=BD·(3/4)³ ………… BOn=BD·(3/4)ⁿ·(1/2) =2·(3/4)ⁿ