I tried to fit a sin function to some data using Statistics[Fit] however the result either didn't work properly or worked differently from the way I expected it to work.

a2 is the calculated function from Statistics[Fit] and a3 is some quickly inserted values that provides a more satisfying result. 

Why is a better fitting line not found?

Download Fitting-Sine-off.mw

To check one of the MythBusters TV episodes, i.e., the fall of a mannequin (80 Kg) from a plane at an altitude of 1200 m in 31 s, with Maple13 (Windows Vista) I solved the following differential equation with initial conditions:

> de:= m*(D@@2)(x)(t) = m*g - k*(D(x)(t))^2:

> ini:= (x(0) = 0, D(x)(0) = 0):


> X:= unapply(rhs(expand(dsolve({de,ini}))),t);

        X := proc (t) options operator, arrow; -m^(1/2)*g^(1/2)*t/k^(1/2)-m*ln(2)/k+m*ln(exp(2*g^(1/2)*k^(1/2)*t/m^(1/2))+1)/k end proc

1) Posing: V0 = sqrt(m * g / k),  T = sqrt(m/(g*k)) one has  V0*T = m/k. I want to have:

   > Xxb:= t -> V0*(- t + T * ln((exp(2*t/T) + 1)/2) ); # m.

 How to obtain this equivalent equation  Xxb(t), without retyping the equation of  X(t) ? With subs , convert or simplify  applied to  X(t), Maple 13 gives error messages.

2) Taking the derivative of  Xxb(t), one find :

     V := proc (t) options operator, arrow; V0*(exp(2*t/T)-1)/(exp(2*t/T)+1) end proc.

How to transform it to V = V0 tanh(t/T) ?

Again, subs , convert or simplify  seem not working, even with  assume(t, real), assume(T, real) ! I know simplify is a difficult task, but Maple should recognize a tanh !

Thank you in advance for any suggestion.

( Note that with m = 80 Kg, g = 9.81 m/s^2 and k = 0.267482 Kg/m, which correspond to a speed limit of V0 =195 km/h, on find t(1200m) = 26 s, instead of 31 s ).

Hi everyone

I am going to add a continious time white guassian noise n(t) to a function f(t), and plot g(t)=f(t)+n(t). Any suggestion?

Also, I am going to filter this white noise, and analysis colored noise. How can I apply a frequency-domain rectangular window to a function?

Thank for your kind answers

Hi everyone

I've come across a RAM-issue.

My program creates a lot of plots using millions of variables-values and it eats up my computers memory since I use the plots to make an animation.

The plots are simple 3d plots created using the surfdata function.

How do I save plots into a single file as the program creates them concurrently such that after the program has terminated I can use the plots to create an animation?

and how do I efficiently delete variables I dont not need anymore?

Dear Friends

            Hope everything going fine with you. I want the numerical solution of nonlinear system of ordinary differential equations using RK method. The system of ODEs and their required results are present in attached file. I am waiting your quick response.

Help.docx

With my best regards and sincerely.

Mob #: 0086-13001903838

how to round all coefficients for a polynomial in short code way?

Does [Length of output exceeds limit of 1000000] mean that the function couldn't be solved and I have to modify the mathematical model?
If the results are just too long to be displayed, how can I see the results?

I am a new guys for Maple. I want know how can I compute this equation.   (x²)^0.5=x.

I think it's simple. But I'm not sure how to impepment in Maple. If you know how to deal with it . Contact me. Thanks

how to make physical quantities graphs from RK45 ode bvp convective boundary layer flow rather than using lines

i use lines command copy one by one yje data from the solution

are they any simplest way to sketch graphs for physical quantities like f'', thetha prime versus 3 parameters?

I want to separate strings into substrings for example
input is "6,3,A,n,k,L,+,-" then the procedure breaks this string into substrings like 
if a member numeric b:="6,3",or if lowercase c:="n", if uppercase l:="A,L" else m:="+,-"
thanks

I try to find the exact (symbolic) value of

(-2*sqrt(7)-4)*EllipticK((1/8)*sqrt(2)*(-3+sqrt(7)))^2+4*EllipticE(-(1/8)*sqrt(2)*(-3+sqrt(7)))*sqrt(7)*EllipticK((1/8)*sqrt(2)*(-3+sqrt(7)))

I tried 'simplify' with different options and 'convert'. It would be pi=3.141... as numerical approximation suggests.

Many thanks.

I think Simpson's rule for integration is very simple and it is just function evaluation over a few points on the interval of integration. So we expect it to be fast.

When I use it as a summation command (using Simpson's formula) it is really fast but when I use the command ApproximateInt with Simpson method it is sometimes really slow. For example

restart;

f := unapply(x^2/(sin(x)+x+1), x);

with(Student[Calculus1]);

evalf(ApproximateInt(f(x), x = 1 .. 2, method = simpson, partition = 20));

or even with partition=10 you must wait for a long time.

Please help.

Thank you

In the running of an example I faced to computation of radical ideal of the following ideal:

<-c*m*u+d*c*n+m*b*v+m*c*t>

I used from Radical command in PolynomialIdeals package. But I dno't now why it's computation is very hard and Time-consuming?

What I have to do? I think there is a bug, since this ideal is simple, apparently.

Maybe an easy question, but which command do I have to use to calculate the difference between e and a list of fractions?

App.mw

Hi all

I don't know why it doesn't work correctly? I want the final answer be in the form of De, U, UN not as beta1 and beta2

Please help me...