Update magloop.html

Added calculated loop area. Added spaces between numbers and units in text.

magloop.html

@@ -549,6 +549,10 @@
                 //fctx.textAlign = "right";
                 const cond_dia = 1.0 * conductor_diameter_slider.value;
                 fctx.fillText("\u2300a = " + cond_dia.toPrecision(3).toString() + " mm", loopx, p1y+2);
+
+                // Write loop area:
+                fctx.textAlign = "right";
+                fctx.fillText("A = " + (Math.PI * dia**2).toPrecision(3).toString() + " m\u00B2", win_width-8, 18);
             }
             
             const aside_canvas = document.getElementById("antennaSide2D");