Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Yes, I phrased it in a wrong way. I meant "simplier", not "easier". The proof is really straightforward once you write down all the definitions. Thanks!
Thank you very much! I was reading "On Smooth Variational Principles in Banach Spaces", by Fabian, Hájek and Venderwerff and they reference the definition to justify this result, so I though it would be much easier. I see it's a bit more complicated. Again, thanks! This was really helpful.