CORRECTION: at 9:12 I seemed to have made an algebra mistake. The corrected acceleration result should be i + j, not i + j. This is a newly made video -- this topic was not covered in my previous playlist. Contact info: @ What's new in 2015? 1. Closed-caption made by myself! -- not the automatic subtitle anymore. 2. Learning objectives added for each video. 3. Quiz questions added -- including end-of assessment questions and preparatory, exploratory questions. 4. Mistakes fixed and cleaned up. 5. New examples/contents for selective videos. My old videos and playlists will still be left on YouTube. Feel free to watch either one. Personally I think the revised videos are better mainly because of the subtitle. Learning objectives of this video: