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I'm not familiar with this area of physics/maths but surely the equation given in the article, ${\displaystyle ii+(a+B\cos t)u=0\ }$ is not correct? Is ${\displaystyle ii}$ supposed to be ${\displaystyle {\ddot {u}}}$ or something else? There's no explaination of what 'i' is and if i is something, why isn't it written as ${\displaystyle i^{2}}$? AlphaNumeric 11:56, 21 October 2007 (UTC) reply