How can I put a line to run from a single point on the x-axis to the top. Like a like that run at x = 5 axis to the top. 

Du plot two lines but overlapped 

how to set color of each line and choose each line plot on top of layer to confirm overlapped?

Not that I care about the virtual rating numbers here, but I am wondering why would one suddenly lose 15 point after posting a problem they found in Maple? Is this typical?

https://www.mapleprimes.com/questions/229443-Why-These-ODEs-Hang-Or-Return-Unsolved

3 hrs ago, I was 3001  and when I came to check on the status if any, now it says 2986.

Just wondering why, that is all. Again, this really does not bother me at all as I do not care about these virtual cloud credit points, and I only post here on occasions and when I found some problem. I just like to know why this happened just now, that is all. 

When I tried these ODE's in Maple 2019, and Maple 2018, they are worked (i.e. gave solutions). Now these ODE's either hang in 2020 or return unsolved. What could have caused this? On Maple 2020, under windows 10:

restart;
ode:=(x^2-1)*diff(y(x),x)^2-y(x)^2+1=0:
dsolve(ode); #hangs

restart;
ode:=(2*x^2+1)*diff(y(x),x)^2+(y(x)^2+2*x*y(x)+x^2+2)*diff(y(x),x)+2*y(x)^2+1=0:
dsolve(ode); # return unsolved

restart;
ode:=x*y(x)^2*diff(y(x),x)^3-y(x)^3*diff(y(x),x)^2+x*(x^2+1)*diff(y(x),x)-x^2*y(x):
dsolve(ode); # return unsolved

restart;
ode:=(diff(y(x),x) = (-y(x)^2+4*a*x)^3/(-y(x)^2+4*a*x-1)/y(x)):
dsolve(ode); #hangs

I noticed that in Maple 2019.2 this problem is also there. But not in Maple 2019.  So something changed from after Maple 2019.

Here is worksheet on Maple 2018 that shows these worked there. But no longer work on Maple 2020. There might be more like these but these the ones I found so far.

issue.mw

Is it possible to define variables with "unit" % or ‰ in Maple?

c:=20%

does not work, it apparently gives you 20 multiplied with the result of the last calculation.

Hi folks!

Is there any way to make this kind of derivative?

If necessary, I can provide the original file here.

Thanks in advance for any help!

If I understand how to use vectors in Maple, I need to give the number of elements.  Is this correct?  I am working with vectors that I do not know the number of elements.  I can use a large number that will be greater than the required number of elements, but this does not seem to be a good solution.  The number of elements is 2000 for about 10 different vectors.  What is the best method to set up the victors for this application?

Can anyone help me to frame the equations in Fractional Reduced Differential Transform Method 

system of nonlinear ordinary differential equations
ds/ dt = b−γ s(t)− (δ s(t)(i(t) + βa(t)) /N − ε s(t) m(t) 
de/ dt = δ (s(t)(i(t) + βa(t))/ N + ε s(t) m(t) − (1−ϑ) θ e(t) − ϑ α e(t) − γ e(t) 
di/ dt = (1−ϑ) θ e(t) − (ρ + γ) i(t)
da/ dt = ϑ α e(t) − (σ + γ) a(t)
dr /dt = ρ i(t) + σ a(t) − γ r(t)
dm /dt = τ i(t) + κ a(t) − ω m(t) 

Good day to all.

I have a function, z(x,y), that I am interested in exploring. The contour plot returns the z-contours on the x-y grid (see attached).

Can anyone suggest a way in which I can now assign z to the vertical axis (instead of y), x to the horizontal axis, and plot the contours for various y-values?

Thanks in advance.

Contour_Plot_MaplePrimes.mw

I'm trying to extract coefficients from an expression that resulted from a matrix cross product operation. Maple inserts a bar above a number of variables (I'm assuming that this is a vinculum). When I use coeff it doesn't recognise the variables with a bar above them as the same as those without a bar above them.

Please help!
 

Download Maple_Issue.mw

Sample code attached with the problem manifesting.

Hi MaplePrimes team,

I am struggling to display a correct projection of a sphere on a tangent plane disc of with Maple’s plot3d, but the resulting grid is not correct somewhere despite of the increasing of number of grids. See picture below:

Fig. 1: The sphere projection on a tangent plane shows a grid problem.

How can I do to fix the problem of undesired grid when the mathematical equation is correct?

Fig. 2: Default 49-grid for Lambert projection showing wrong grids.

To increase the number of grids such that grid = [1000, 1000], grid = [2000, 2000] or higher, or the idea of removing just one row grid row or one column grid like [299, 299] changes absolutely nothing. It still results some crossing meshes that hide desired projected map.

Even the use of the option numpoints fails.

Fig. 3: Higher grid for Lambert projection showing wrong grids.

Here, my parametric equations:

- The sphere equation is

S := (θ,φ)-> R * e_r(θ,φ)

            Where,

The unit radial vector (US coordinates system) is:

e_r := (θ,φ)-> cos(θ) *cos(φ) * ex + cos(θ) *sin(φ)  * ey + sin(θ) * ez:

ex := <1,0,0>:          ey := <0,1,0>:           ez := <0,0,1>:

- θ: latitude or elevation variable;

- φ: longitude or azimuthal variable

- R is the radius

Then,

- The projection on plane (Lambert projection) is

P := (θ,φ)-> X₀ + R*α(θ,φ)*e_ρ(θ,φ):

Where

X₀ := S(θ₀, φ₀)   Free tangent point belonging both to the sphere and the plane disc.

α := (θ,φ)-> arccos( cos(φ - φ₀)*cos(θ)*cos(θ₀) + sin(θ)*sin(θ₀) ):

α is the arc angle of radius R between X₀ and any point on the sphere.

e_ρ := (θ,φ)-> e_N(θ,φ) &x e_r0:            Crossproduct

e_ρ is the polar direction from fixed point X₀ to any point X = S(θ,φ)  on the sphere

e_N := (θ,φ)-> if          evalf(abs(φ - φ₀) - π) = 0 then

e_θ0   #Arbitrary elevation unit vector, but unimportant now.

else      UNITVECTOR(e_r0 &x e_r(θ,φ))

                                   fi:

Where,

- The unit tangential elevation vector

e_θ0 :=-sin(θ₀)*cos(φ₀) * ex - sin(θ₀)*sin(φ₀) * ey + cos(θ₀) * ez:

- The unit radial vector at X₀

e_r0 := e_r(θ₀, φ₀) 

Note that implicitplot3d-based method is not really preferred here because it is very high cost in grids unlike the parametric equation method which responds in few seconds at high grid number ~2000 with modern computer.

My Goal:

My final objective is to plot a world map projection of the Earth called Lambert Azimuthal Equal-Area (abbreviated LAEA) projection following any geographic coordinates involving the latitude = φ and the longitude = λ, all input angle can be in degree angle, but internally compiled in radian.

For that, I insert an initial equirectangular projection of world map in the Maple’s plot3d option.

Fig. 4: Initial equirectangular projection of world map (low 500-pixel image for test and large 1000-pixel or higher resolution for definitive image).

The astute now is to arrange the ranges such that the surface equation is defined on

ϕ = -π/2...π/2     and    λ = 0..2π

And taking account the image scanning (Width x Height) have to be swept however in the range:

λ = 0..2π    then    ϕ = 0..π,

Then, I get this instruction without to detail all options:

plot3d(S(ϕ - Pi/2, g(λ - Pi)), λ = 0..2*Pi, ϕ = 0..Pi, image = “C:\....\World_map.jpg”, …)

where g is a longitudinal λ-periodic function on 0..2π in the objective to keep the continuity of the map at any longitude.

Here, the first result of LAEA projection at φ = 0 and λ = 0

(a)

Fig. 5: LAEA projection near latitude = 0 and longitude = 0 shows negligible grid failure at circular edge.

So now, the problem begins worse when input begins far from (0°,0°), for instance (60°, -90°).

In fact, the overall resulting map seems to be correct, but it is unfortunately hidden by an unnecessary secondary grid layer trending an undesirable shortcut grid lines explained at the beginning of this report.

Fig. 6: Wrong grids seem to be the source of mask problem for LAEA projection at any φ, λ.

Thank you for your time.

Best.

Guy.

Here the full PDF report:

Problem_of_grid_option_in_plot3d_-_by_Guy_April_27th_2020.pdf

How can I  get the "phase portrait including vector fields" and several trajectories of the following dynamical system in the polar coordinates (Note that the system is also in polar coordinate)??

(-(2*I)*c1*eta+c1*sqrt(-e0^2-4*eta^2))/e0 = c2, ((2*I)*c2*eta+c2*sqrt(-e0^2-4*eta^2))/e0 = -c1

How can we remove c1 from the expression of c2 and similarly c2 from c1?

Hi

I try to visualize and animate the hollow volume between two functions, but I do not have an optimal rendering

Ideas? Thanks

,Q1.mw

The worksheet below displays dual cones inside the unit sphere, but the Gauss-Bonnet formula (area of upper cone's spherical cap plus length of dual cone's intersection with unit sphere) does not equal 2*Pi.

Please find my error.

Dual_cones.mw