To further simplify the expression, we perform the following approximations: b → → 0 ; V 0 → → ∞ ∞ ; V 0 b = c o n s t a n t ⇒ ⇒ β β 2 b = c o n s t a n t ; α α 2 b → → 0 ⇒ ⇒ β β b → → 0 ; sin ⁡ ⁡ ( β β b ) → → β β b ; cos ⁡ ⁡ ( β β b ) → → 1.