Degree
is not a function--rather it is a parameter. So you do not want Degree@,
(i.e., no @
) and also yo want to divide by Degree
in your definition of degree
as in the following:
Manipulate[
With[{degree = \[Phi]/Degree},
Graphics@Text[ToString[degree]]], {{\[Phi], 45 Degree}, 0 Degree,
90 Degree}]
In this I also localized your definition of degree
using With
as well as removed the unnecessary Show
.