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function computeField(input) {
  if (input.value != null && input.value.length != 0)
      input.value = "" + eval(input.value);
  computeForm(input.form);
}

function computeField2(input) {
    if (input.value != null && input.value.length != 0)
        input.value = "" + eval(input.value);
    computeForm2(input.form);
}


function computeForm(form) {
//The formula is: hp = weight * (speed / 234)3 
//The Formula is: ET = hp/weight * 197
	
	var a = form.weight.value;
	var b = form.trap.value / 1.6;
	var c =	b / 234;	
	var d = c * c;
	var e = d * c;
	var f = a * e;
	
    form.hp.value = f
}

function computeForm2(form) {
	var a = form.weight2.value;
	var b = form.trap2.value;
	var c = a / b;
	var d = Math.pow(c,1/3);
	var e = d * 5.825;
	form.hp2.value = e; 
	
	var f = b / a;
	var g = Math.pow(f,1/3);
	var h = g * 234;
	form.trap3.value = h * 1.6;
	
}

<!-- done hiding from old browsers -->