I'm not sure if this is fixed in newer Maples or if there's a work around. 

Whenever I size a 3d plot, that I'm trying to stretch out the width while keeping the height, never seems to work.  For example using the size=[3000,800] produces a plot area that's bigger but NOT actually a plot stretched in the x axis.  Going to size=[3000,3000] of course then makes the plot and the area bigger and so scales both x and y bigger.  However I don't want the y axis scaled up - I'm trying to scale the plot up - not the area.  And what happened to the window zoom, icon - we've lost zoom control to just magnify + and magnify - (at least in 2022) this seems like a regression. 

Is this plot size a bug or just a plot command that fails to function like it should? 

Hi everyone, I am trying to plot graphs for dp/dx versus x from my ordinary differential equation numerically. My file is working, but the outcome is straight lines, which means I am doing something wrong. Could anyone  please have a look on my file.

Help-dpdx.mw

the expected  results should be  look like this

I am very confused by the y-value of the rightmost point on the plot below.

Download plotq.mw

I have a question about a calculation I was just trying to do. For some context, I am trying to calculate the pH of a solution of a weak acid in water. When the concentration of the weak acid is low enough, we need to consider the effect of ionization of the water itself (ie, autoprotolysis of water), since the order of magnitude of this ionization is the same as the order of magnitude of the ions due to the weak acid in this case of very low concentration.

There is a specific formula that can be used for this, which is shown below.

K_a is a constant that depends on the weak acid being considered, and K_w is a constant as well (for the autoprotolysis of water). I am interested in solving for the concentration of hydronium, given an initial concentration of the weak acid [HA]_initial.

I'd like to solve the equation for different values of [HA]_initial.

Download concentrations.mw

Today I was working on some plots involving pH, which is defined as -log_10 ([hydronium]), that is, the negative of the base 10 logarithm of the concentration of hydronium in a solution.

I reached an expression for a variable x that is a function of an initial concentration C_i.

I wanted to plot the pH given by -log_10 (0.0001+x).

Note that x(0)=0, and so for this latter plot we should have the point (0, 4).

I am not able to see any part of the plot near (0,4), as can be seen below.

Download plotatzero.mw

I aim to conduct a numerical frequency sweep analysis on a nonlinear, coupled two-degree-of-freedom vibration model and compare the results with the analytical solution. However, I am currently facing two main difficulties:

1. I am unsure how to determine whether the computed response has reached a steady state. If I simply use the maximum value to represent the steady-state amplitude, it can be misleading—since transient responses prior to reaching steady state may yield a higher peak, as seen in the uploaded code.

2. I do not know how to properly select the steady-state result from the previous frequency as the initial condition for the next frequency step.
   2.mw

Approximation_of_ODEs_with_Cubic_Splines.mw

Hi!

I am studying Burger's equation, and I would like to see the steps that Maple takes to solve this.  "ShowSteps" doesn't seem to work.

Unfortunately, I am unable to share the worksheet I made.

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How do we simplify the arguments of the exponential in (1)? Further how to express (1) into hyperbolic/trig functions? 
 

Download argument.mw

I am taking a course in quantum mechanics and trying to do the calculations in Maple.

In the worksheet below I try to solve a system of equations to find some constants. 

It isn't very relevant that the domain is physics. 

The issues I have are with manipulations of expressions (specifically, simplifications).

Download solve_constants.mw

In reality, I would like to the entirety of sqrt(2m(E-V__0)/hbar) a variable by the name of s.

Download simplify_roots.mw

Below is a simple demonstration of something that I am very confused about in another worksheet I am working on.

Basically, I have a function of x called psi_I and I want to define another function of x called psi_I,d which is just the derivative of psi_I.

In, the snippet below, this works if I use the variable names psi_1 and psi_1,d, but not if I replace the "1" with a "I" as I want to do.

In addition, I don't know why the output (6) is different from (7) or (8). All three are from the same command in Maple.

Download psi_subscript.mw

Download evcalc.mw

The document below is long because I go through the context of my question step-by-step. 

The context is solving a first-order system of differential equations where we have complex eigenvalues.

But essentially, my question has to do with the end of this reasoning. I find four solutions x1, x2, x3, and x4, and I would like to check whether they are indeed solutions by subbing them into the original system x'=Ax.

When we make such a substitution, we get an equation of the form yl=yr, where yl and yr are 4x1 vectors. If the equality is true then we can say we have a solution.

My question is about how to check for this equality. I amusing Maple's "Equals" but this doesn't seem to work for all four solutions.

Download evs_equal.mw

Dear Maple Community,

I come to you with a question about the reduced involutive form (rif) package. Namely, I decided to try the classic example from the "LONG GUIDE TO THE STANDARD FORM PACKAGE", which dates back to 1993. Here is the link to the complete documentation:

https://wayback.cecm.sfu.ca/~wittkopf/files/standard_manual.txt

So, the example is the following:

2.1 SIMPLE EXAMPLES

EXAMPLE A

Consider the system of nonlinear PDEs:       

y Zxxx - x Zxyy  =  Zyy - y Zy

                        2     2    2
2 y x Zxxx Zxyy + x Zxxx + x y Zxyy  =  0

                  2    2
y Zxyy - x W + 2 x  y Z  =  0

                 2    2
Zyy - y Zy  + 2 x  y W  =  x W

where the dependent variables W and Z are functions of the
independent variables x and y, and Zxxx denotes the third partial
derivative of Z with respect to x etc.

After making computations back in 1993 with Maple V, they obtain the following involutive form:

In our original notation the (considerably) simplified system is:
                                            2
  Zxxx = 0, Zxy = 0, Zyy = y Zy, W = 2 x y Z

So, I tried the same system of PDEs in the modern Maple and the modern rifsimp() command. You can find the result below:

I demo_question.mw

The problem is that nowadays [Maple 2022.1] , I get only the trivial solution: z = 0 and w = 0.

Could someone clarify, please, where the truth is and what am I doing wrong?

Thanks a lot in advance for any help and clarification!

Best regards,

Dr. Denys D.