P_survive(nτ) = [cos²(Γτ)]ⁿ → e^(-Γ²τT)
After each measurement finding the system undecayed, survival probability resets. With interval τ over total time T:
P_Zeno = cos²ⁿ(Γτ) ≈ (1-Γ²τ²)^(T/τ) → e^(-Γ²τT)
As τ→0, effective decay Γ_eff = Γ²τ→0. The quantum Zeno effect shows measurement itself has physical consequences.