Derivative notations at a given point
f'(a) = y'|_{x=a} = \cfrac{df}{dx}\substack{ \vert \\ \vert \\ \vert }_{x=a} = \dfrac{dy}{dx} \substack{ \vert \\ \vert \\ \vert }_{x=a}
or
f'(a) = y'|_{x=a} = \cfrac{df}{dx}\substack{ \vert \\ \vert \\ \vert }_{x=a} = \dfrac{dy}{dx} \substack{ \vert \\ \vert \\ \vert }_{x=a}
or