Drop redundant variable.

d3.js

@@ -6475,7 +6475,7 @@
     }
   };
   function d3_geo_areaRingStart() {
-    var λ00, φ00, λ1, φ1, λ0, φ0, cosφ0, sinφ0;
+    var λ00, φ00, λ1, λ0, φ0, cosφ0, sinφ0;
     d3_geo_area.point = function(λ, φ) {
       d3_geo_area.point = nextPoint;
       λ1 = λ0 = (λ00 = λ) * d3_radians, φ0 = (φ00 = φ) * d3_radians, cosφ0 = Math.cos(φ0), 
@@ -6489,7 +6489,7 @@
         var dλ = λ - λ0, cosdλ = Math.cos(dλ), d = Math.atan2(Math.sqrt((d = cosφ * Math.sin(dλ)) * d + (d = cosφ0 * sinφ - sinφ0 * cosφ * cosdλ) * d), sinφ0 * sinφ + cosφ0 * cosφ * cosdλ), s = (d + π + φ0 + φ) / 4;
         d3_geo_areaRing += (dλ < 0 && dλ > -π || dλ > π ? -4 : 4) * Math.atan(Math.sqrt(Math.abs(Math.tan(s) * Math.tan(s - d / 2) * Math.tan(s - π / 4 - φ0 / 2) * Math.tan(s - π / 4 - φ / 2))));
       }
-      λ1 = λ0, φ1 = φ0, λ0 = λ, φ0 = φ, cosφ0 = cosφ, sinφ0 = sinφ;
+      λ1 = λ0, λ0 = λ, φ0 = φ, cosφ0 = cosφ, sinφ0 = sinφ;
     }
     d3_geo_area.lineEnd = function() {
       nextPoint(λ00, φ00);

src/geo/area.js

@@ -25,7 +25,7 @@ var d3_geo_area = {
 };
 
 function d3_geo_areaRingStart() {
-  var λ00, φ00, λ1, φ1, λ0, φ0, cosφ0, sinφ0; // start point and two previous points
+  var λ00, φ00, λ1, λ0, φ0, cosφ0, sinφ0; // start point and two previous points
 
   // For the first point, …
   d3_geo_area.point = function(λ, φ) {
@@ -62,7 +62,7 @@ function d3_geo_areaRingStart() {
     }
 
     // Advance the previous points.
-    λ1 = λ0, φ1 = φ0, λ0 = λ, φ0 = φ, cosφ0 = cosφ, sinφ0 = sinφ;
+    λ1 = λ0, λ0 = λ, φ0 = φ, cosφ0 = cosφ, sinφ0 = sinφ;
   }
 
   // For the last point, return to the start.