function GeoCalc(){
var Surface;
sidea = eval(document.weidthelic.sidea.value);
sideb = eval(document.weidthelic.sideb.value);
spire = eval(document.weidthelic.spire.value);


if((sidea > 0)  && (sideb > 0) && (spire > 0)){

	Surface = FormatNumber(Math.sqrt(Math.pow(Math.PI,2) * Math.pow(spire,2) * Math.pow(sidea,2) + Math.pow(sideb,2)));
	
	document.getElementById("surface").innerHTML = "&#928; = 3.141592653589793<br />Longeur<br />" + Surface + "  cm<br />" + FormatNumber(Surface/100) + "  m<br />";
}

}