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2d
comment Ordinary Differential Equation - Initialising conditions
Its a simple syntax error. Instead of your code you should write DSolve[{n'[t] == r n[t] (1 - (n[t]/k)), n[0] == n0}, n[t], t] . The difference is in n0 , rather than n_0 . With this correction you will get the answer n[t] -> (E^(r t) k n0)/(k - n0 + E^(r t) n0) . The underscore is reserved in Mma.
2d
answered Solving Differential Algebraic Equations as BVP
Oct
22
comment How find solve the equation complex conjugate?
Are you sure that it is a Mathematica question, rather than a mathematical one. Indeed representing z=r Exp[I a] and substituting it into your equation one immediately gets a trivial solution r=0 and one non-trivial: r=Exp[-3 a I]with the requirement that both the left- and the right-hand sides are real. The latter gives you a=2 Pi/3 and r=1 .
Oct
22
comment Partial fraction decomposition of $1/(e^x-1)$
Define please, what is CAS?
Oct
14
comment Plot3D and NIntegrate issues
Indeed, Integrate[2*x - y, {x, -1*Sqrt[4 - y^2], Sqrt[4 - y^2]}, {y, -2, 2}] gives 0 , while NIntegrate with the same content returns an error meaasge on my machine Win7 Mma10.0. It looks like a bug for me.
Oct
13
awarded  Excavator
Oct
13
reviewed Reject and Edit suggested edit on Generate random points in a region with higher probability in a sub-region
Oct
13
revised Generate random points in a region with higher probability in a sub-region
added 8 characters in body
Oct
10
comment Dynamic interaction with a 3D plot
@Ojtwist Rationalize substitutes rational numbers instead of the decimal ones. It is not necessary, but Mma works faster in that case and the expressions look less awful. For the second question check please Menu/Help/AxisLabels
Oct
10
answered Dynamic interaction with a 3D plot
Oct
8
answered Outputting numbers symbolically
Oct
3
answered How can I get Solve to combine Sin/Cos into Tan?
Oct
2
answered Mathematica doesn't know the answer to this differential equation system
Oct
2
comment Mathematica doesn't know the answer to this differential equation system
Depends upon your goal. May be you could simplify it a bit, to help Mma. You may think about solving it numerically. Then you need to somehow fix the values of the constants.
Oct
2
comment Mathematica doesn't know the answer to this differential equation system
Mma returns the same code, if it does not know the solution.
Oct
1
awarded  Nice Answer
Oct
1
comment Using variable values from Manipulate in later Plots etc
It just returns us to my comment.
Oct
1
comment Definite Integral over Bessel Function
If Mma returns the input, it means that it cannot solve the task you gave it. Either you should live with it, or you may try to change the statement of problem. For example, in some problems one cannot solve the integral using Integrate, but NIntegrate works.
Oct
1
answered Spherical parametric plot
Oct
1
revised Manipulate with Locator question
added 396 characters in body