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

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

	Surface = FormatNumber(Math.sqrt(Math.pow(sidea,2) + Math.pow(sideb,2)));
	
	document.getElementById("surface").innerHTML = "Diagonale<br />" + Surface + "  cm<br />" + FormatNumber(Surface/100) + "  m";
}

}