¿How can I prove, using a sequence of mollifiers, that the set $C^{\infty}_{c}(I)$ (also known as $\mathcal{D}(I)$) is dense in $W^{1,p}_{0}(I)$?
Also I want to know that if $u\in W^{1,p}(I)\cap C_{c}(I)$ then $u\in W^{1,p}_{0} (I)$
Here $I\subset\mathbb{R}$ a open interval.
¿Could help me by computing an unconventional example?