Talk:Parametric resonance

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