Petit calcul avec javascript

je vous donne le java script
en esperrant que vous pouvez m'aider

<script language="JavaScript">

function parseNum( val )
{
re = /,/g;
return parseFloat( val.replace( re, '.' ) );
}

function numFormat( val )
{
re = /\./g;
bla = "" + Math.round( val * 100 ) / 100;
if( bla == "NaN" )
bla = ""
return bla.replace( re, ',' );
}

function calc( form2 )
{

DRi = parseNum( form2.DRi.value ); <!-- Diamétre Rotor interieur -->
EpA = parseNum( form2.EpA.value ); <!-- Epaisseur Aimant -->
Eas = parseNum( form2.Eas.value ); <!-- Espace aimant stator -->
La = parseNum( form2.La.value ); <!-- largeur Aimant -->
L = parseNum( form2.L.value ); <!-- somme de Rs Eas EpA -->
Dla = parseNum( form2.Dla.value ); <!-- Demi La -->
RRi = parseNum( form2.RRi.value ); <!-- Rayon Rotor interieur -->
Rs = parseNum( form2.Rs.value ); <!-- Rayon stator -->
Dr = parseNum( form2.Dr.value ); <!-- Diametre Rotor -->

Dla = ( La/2 ) ; <!-- moitier de La -->
Rs = ( Dr/2 ) ; <!-- rayon stator -->
L = Rs+Eas+EpA ; <!-- somme RsEasEpA -->
RRi = Math.sqrt((L*L)+(Dla*Dla)) ; <!-- diametre interieur rotor -->
DRi = ( RRi*2 ) ; <!-- Diametre rotor interieur -->

form2.Dr.value = numFormat( Dr );
form2.EpA.value = numFormat( EpA );
form2.EaS.value = numFormat( EaS );
form2.La.value = numFormat( La );
form2.DRi.value = numFormat( DRi );
form2.Dla.value = numFormat( Dla );
form2.Rs.value = numFormat( Rs );
form2.RRi.value = numFormat( RRi );
form2.L.value = numFormat( L );

}

</script>

<h2 align="center">Pour usiner le rotor </h2>
<h2 align="center">un petit calcul</h2>
<h2 align="center"> pour trouver le diametre interieur</h2>
<h2 align="center"><br>
</h2>
<p>

</p>
<pre><form name="form2">
<div align="right">
<p><b> Dr<sub></b>= <font color="#0000ff">Diamétre rotor </font><input size="6" name="Dr" onchange="calc( this.form )" type="text">[mm]
<b> EpA<sub></b> = <font color="#0000ff">Epaisseur aimant </font><input size="6" name="EpA" onchange="calc( this.form )" type="text">[mm]
<strong>EaS</strong> = <font color="#0000ff">Espace Aimants/Stator </font> <input size="6" name="EaS" onchange="calc( this.form )" type="text">[mm]
<b>La</b> = <font color="#0000ff">Largeur Aimants </font> <input size="6" name="La" onchange="calc( this.form )" type="text">[mm]
<p><b>DRi</b> = <font color="#0000ff">Diametre interieur rotor </font> <input size="6" name="DRi" readonly="readonly" class="RESULT" type="text">[mm]
</p></div>