What is the expression for the digital frequency when r=1?

• A. \(\frac{1}{T} tan⁡(\frac{ΩT}{2})\)
• B. \(\frac{2}{T} tan⁡(\frac{ΩT}{2})\)
• C. \(\frac{1}{T} tan^{-1}(\frac{ΩT}{2})\)
• D. \(\frac{2}{T} tan^{-1}⁡(\frac{ΩT}{2})\)