- #1

- 18

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[tex]\frac{dr}{dt} = \Phi - \Psi \frac{2}{r}\frac{dr}{dt}[/tex]

I first collect the derivative terms together and integrate the equation with respect to r and t to obtain

[tex]r + 2\Psi\ln{r} = \Phi{t} + r_0 [/tex]

where r0 is the constant of integration. My question is how would I make r the subject of the above equation?

Many thanks.