7.16.3 Can you answer these questions?

7.16.3.1 Excess lines in the solution plot of vector ODE

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=245826

I've got an ODE system, which I attempt to solve by two ways: solving the system itself, and using vector ODE. 
Here is code of first way: 
... 
[plotting] [differential-equations] [vector] [vector-calculus]
 

asked by Cpp Nosavvier https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=79893 3 votes

7.16.3.2 Algorithmically imposing a substitution in a difficult integral

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=245884

Consider the following integral: 
$$I = \frac{1}{\pi c^2} \int\limits_{r=0}^c 2 \pi r\ e^{-\frac{ \left( \sqrt{a^2 - r^2} -\sqrt{b^2 - r^2} \right)}{\lambda}}\ dr$$ 
under the conditions $a>b>c>... 
[calculus-and-analysis] [replacement]
 

asked by David G. Stork https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9735 2 votes

7.16.3.3 How to expand a rational function as a single fraction

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=245673

This has been annoying me for a long time. I want a rational function to be represented in the form 
$$\frac{a_nx^n+....a_0x^0}{b_mx^m+....b_0x^0}$$ 
But this seems to be quite difficult. Mathematica ... 
[simplifying-expressions]
 

asked by grdgfgr https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=28163 2 votes

answered by Ulrich Neumann https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=53677 0 votes