Following the same approximations as above ( b → → 0 ; V 0 → → ∞ ∞ ; V 0 b = c o n s t a n t ), we arrive at cos ⁡ ⁡ ( k a ) = cosh ⁡ ⁡ ( α α a ) + P sinh ⁡ ⁡ ( α α a ) α α a with the same formula for P as in the previous case ( P = m V 0 b a ℏ ℏ 2 ) .