I'm brushing up on calculus. I don't see how this derivative works.(adsbygoogle = window.adsbygoogle || []).push({});

x(t) = A cos(ωt-[itex]\varphi[/itex])

v(t) = dx / dt = - Aωsin(ωt+[itex]\varphi[/itex])

I get that the derivative of cosx is -sinx. I get that the omega is brought outside the cos function because of U substitution.

Why does the the minus sign turn into a plus sign?

Btw I saw this on wikipedia: http://en.wikipedia.org/wiki/Simple_harmonic_motion

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# Quick Calc Correction

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