The problem you are facing is that the `FullForm`

of `x/2`

changes in the assessment, combined with `HoldAllComplete`

attribute of `MakeBoxes`

:

```
Hold(a/2)//FullForm
(* Hold(Times(a,Power(2,-1))) *)
a/2//FullForm
(* Times(Rational(1,2),a) *)
```

Note how $ a cdot2 ^ {- 1} $ changes made to $ a cdot frac $ 12 when he is allowed to evaluate. As mentioned above, this leads to problems due to the `HoldAllComplete`

attribute of `MakeBoxes`

: You define a rule for the form that you enter, which means that it will not be applied to the evaluated form:

```
MakeBoxes(Sin(Subscript(α, i) / 2), StandardForm) =
MakeBoxes(Subscript(s, Subscript(Overscript(α, _), 2)), StandardForm)
Sin(Subscript((Alpha), i)/2)
```

$ sin ( frac alpha2) $

```
HoldForm(Sin(Subscript((Alpha), i)/2))
```

$ s _ { bar { alpha} _2} $

To resolve this problem, you must define a formatting rule for the evaluated form:

```
MakeBoxes(Sin(Rational(1, 2) Subscript(α, i)), StandardForm) =
MakeBoxes(Subscript(s, Subscript(Overscript(α, _), 2)), StandardForm)
Sin(Subscript((Alpha), i)/2)
```

$ s _ { bar { alpha} _2} $

You can also inject the evaluated form into `MakeBoxes`

:

```
With(
{evaluated = Sin(Subscript(α, i) / 2)},
MakeBoxes(evaluated, StandardForm) =
MakeBoxes(Subscript(s, Subscript(Overscript(α, _), 2)), StandardForm)
)
Sin(Subscript((Alpha), i)/2)
```

$ s _ { bar { alpha} _2} $

Note that the use `Evaluate`

would not work because `HoldAllComplete`

prevents any form of evaluation, including `Evaluate`

and up-values.