need to use EJS_5.1_150302 to avoid bug of graphic not refreshed http://weelookang.blogspot.sg/2015/07/ejss-vector-sum-model.html Designed by Fu-Kwun Hwang http://www.phy.ntnu.edu.tw/ntnujava/ http://weelookang.blogspot.sg/2010/06/add-two-vectors-to-determine-resultant.html Original Source code by Fu-Kwun Hwang http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=216.msg846#msg846 Derived work by Wee Loo Kang under creative commons http://creativecommons.org/licenses/by/2.5/tw/deed.en

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