Why is the absolute value of sinx used in the integral of cotx? • Physics Forums

Vividly · 2022-01-13T11:15:15+00:00

Why is there a absolute value sign on sinx? Does it have to do with the domain of cot x and sin x?

Thread 'How does time derivative commute from one variable to another?'

I'm reviewing Meirovitch's "Methods of Analytical Dynamics," and I don't understand the commutation of the derivative from r to dr: $$ \mathbf{F} \cdot d\mathbf{r} = m \ddot{\mathbf{r}} \cdot d\mathbf{r} = m\mathbf{\dot{r}} \cdot d\mathbf{\dot{r}} $$

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I Why is the absolute value of sinx used in the integral of cotx?

Thread 'How does time derivative commute from one variable to another?'

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