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;
		}