Why is $\overline{\mathbb{F}_p}((t))$ transcendental over $\mathbb{F}_p((t))$ ?
I guess $\overline{\mathbb{F}_p}((t))$ is not unramified over $\mathbb{F}_p((t))$ because $\overline{\mathbb{F}_p}((t))$ is transcendental over $\mathbb{F}_p((t))$・・・①.
But why ① holds? I couldn't check ① by myself. What element is transcendental element? And why? (In general, to prove transcendentality exactly is difficult, is it managable in this case?)