function GeoCalc(){
var Volum;
sidea = eval(document.torevol.sidea.value);
sideb = eval(document.torevol.sideb.value);

if(sidea < (sideb * 2))
	document.getElementById("volume").innerHTML = "Calcul impossible !";

if((sidea > 0) && (sideb > 0) && (sidea >= (sideb * 2))){

	Volum = FormatNumber((2 * Math.pow(Math.PI,2)) * ((sidea / 2) - (sideb / 2)) * Math.pow((sideb / 2),2));
	
	if(Volum >= 10000)
		resultVolum = "&#928; = 3.141592653589793<br />Surface<br />" + Volum + "  cm<sup>2</sup><br />" + FormatNumber(Volum/1000000) + "  m<sup>2</sup><br />";
	else
		resultVolum = "&#928; = 3.141592653589793<br />Surface<br />" + Volum + "  cm<sup>2</sup><br />";
	
	document.getElementById("volume").innerHTML = resultVolum;
}

}