function calc_square (height, width) {
	var h = parseFloat (height);
	var w = parseFloat (width);
	return Math.ceil (h * w);
}
function calc_circle (diam) {
	var d = parseFloat (diam);
	var r = d * 0.5;
	return Math.ceil ((r * r) * 3.1452);
}
function calc_tri (base, height) {
	var b = parseFloat (base);
	var h = parseFloat (height);
	return Math.ceil (b * h * 0.5);
}
function do_square () {
	var h = document.area_form.height.value;
	var w = document.area_form.width.value;
	document.area_form.area.value = calc_square (h, w);
	return false;
}
function do_circle () {
	var d = document.area_form.diam.value;
	document.area_form.area.value = calc_circle (d);
	return false;
}
function do_triangle () {
	var b = document.area_form.base.value;
	var h = document.area_form.theight.value;
	document.area_form.area.value = calc_tri (b, h);
	return false;
}