Errata: Reverse sine/cosine in example to match book text. (no visual…

… effect on demo)

errata.md

@@ -37,6 +37,18 @@ abstraction (submitted by Peter Stema), and the book omits
 the line where the angle is incremented each frame
 (submitted by Steve Paget).
 
+### p. 60, p. 61
+
+In examples `08-circle.html` and `09-oval.html`, to match
+the text above, the sine and cosine functions should be
+reversed when calculating the ball's position. (Submitted by
+Gerald Cullen)
+
+~~~
+ball.x = centerX + Math.cos(angle) * radius;
+ball.y = centerY + Math.sin(angle) * radius;
+~~~
+
 ### p. 67
 
 Typo in the last sentence, it should read: *You should have

examples/ch03/08-circle.html

@@ -28,8 +28,8 @@
         window.requestAnimationFrame(drawFrame, canvas);
         context.clearRect(0, 0, canvas.width, canvas.height);
 
-        ball.x = centerX + Math.sin(angle) * radius;
-        ball.y = centerY + Math.cos(angle) * radius;
+        ball.x = centerX + Math.cos(angle) * radius;
+        ball.y = centerY + Math.sin(angle) * radius;
         angle += speed;
         ball.draw(context);
       }());

examples/ch03/09-oval.html

@@ -29,8 +29,8 @@
         window.requestAnimationFrame(drawFrame, canvas);
         context.clearRect(0, 0, canvas.width, canvas.height);
 
-        ball.x = centerX + Math.sin(angle) * radiusX;
-        ball.y = centerY + Math.cos(angle) * radiusY;
+        ball.x = centerX + Math.cos(angle) * radiusX;
+        ball.y = centerY + Math.sin(angle) * radiusY;
         angle += speed;
         ball.draw(context);
       }());