Kleppner and Kolenkow's Introduction to Mechanics text on page 241 (1st edition) has:(adsbygoogle = window.adsbygoogle || []).push({});

[itex]\frac{d}{dt}[/itex](r^{2}[itex]\dot{\theta}[/itex])=r(2[itex]\dot{r}[/itex][itex]\theta[/itex]+r[itex]\ddot{\theta}[/itex])

Is this wrong or am I missing something? I get:

r(2[itex]\dot{\theta}[/itex]+r[itex]\ddot{\theta}[/itex])

...by product rule. It seems at the least the book should have a theta dot in the first term. I don't see where the r dot comes from though. Thank you.

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# Homework Help: Derivative related to equal areas proof

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