var E=0;
var I=0;
var R=0;
var P=0;
function clearBoxes(form)
{
	form.E.value="";
	form.I.value="";
	form.R.value="";
	form.P.value="";
	form.E.focus();
}
function showresults(form)
{
	form.E.value=E;
	form.I.value=I;
	form.R.value=R;
	form.P.value=P;
}
function solve(form)
{
	var i=4;
	if(!form.E.value) E=0;
	else E=eval(form.E.value);
	if(E==0) i--;
	if(!form.I.value) I=0; 
	else I=eval(form.I.value);
	if(I==0) i--;
	if(!form.R.value) R=0;
	else R=eval(form.R.value);
	if(R==0) i--;
	if(!form.P.value) P=0;
	else P=eval(form.P.value);
	if(P==0) i--;
	if(i==0) return;
	if(i !=2)
	{
	alert("\nError. Please enter 'two' values.\n");
	return;
	}
	if(E !=0)
	{
	if(I !=0)
	{	
	R=E/I;
	P=E*I;				
	}
	else if (R !=0)
	{
	I=E/R;
	P=(E*E)/R;				
	}
	else if (P !=0)
	{
	I=P/E;
	R=(E*E)/P;				
	}
	showresults(form);			
	form.E.focus();
	return; 
	}
	if(I !=0)
	{
	if (R !=0)
	{				
	E=I*R;
	P=(I*I)*R;				
	}
	else if (P !=0)
	{		
	E=P/I;
	R=P/(I*I);			
	}
	showresults(form);			
	form.I.focus();
	return;
	}	
	I=Math.sqrt(P/R);
	E=Math.sqrt(P*R);			
	showresults(form);			
	form.R.focus();
	return;
}
// end Calculation: electric power, voltage, current, and resistance -->