Calculates the annual effective discount rate (d) from the effective interest rate (i).
Formula: d = i / (1 + i)
The effective annual interest rate (e.g., 0.05 for 5%)
The effective discount rate
Error if i ≤ -1 (invalid for discount rate computation)
Calculates the annual effective discount rate (d) from the effective interest rate (i).
Formula: d = i / (1 + i)