# User Portlet Gianluca Gorni
Discussions
Have you any reason to think that there exist nontrivial solution to your equations? This plot may suggest that the only solution may be x==0, except for periodicity: eqs = Rationalize[{Sin[x]*Cos[2.5*y]*Cosh[2.5*z] + ...
You can do a lot this way: sol = NDSolveValue[{D[r[t], t] == (r[t].r[t])^-1 RotationMatrix[Pi/2, {0, 0, 1}].r[t], r == {1, 1, 1}}, r, {t, 0, 1}] sol
The solution set is more complicated than that: Reduce[(js + ps) 6 == w && js (pd + 5) == w && ps pd == w, Reals] // LogicalExpand I don't know the exact reason why Solve gives an empty set in that special case, but with slight...
The code pp/.Line[x_]:>{Arrowheads[Table[.04, {4}]], Arrow[x]} targets the hidden internal structure of the output of Plot and ParametricPlot. Try Plot[x,{x,0,1}][] you will see that it contains a Line primitive, which...
Each of the points has integer distance from the others. This finds a new point with integer distances from the other four: pts = {{0, 0}, {20, 0}, {138/5, (24 Sqrt)/5}, {25, 10 Sqrt}}; dists = MapIndexed[({x, y} - #) . ({x, y} - #)...
Have you tried with parentheses: Cases[{"u1", "p1"}, _?(StringStartsQ[#, "u"] &)] Cases[{"u1", "p1"}, _?(StringStartsQ["u"])]
Maybe the wireframe version is clearer: Plot3D[2 x^2 y/(x^4 + y^2), {x, -1, 1}, {y, -1, 1}, PlotPoints -> 200, Exclusions -> Automatic, MeshFunctions -> {#2/#1 &}, Mesh -> {Tan[Pi/2 Range[-19, 19]/20]}, PlotStyle -> None]
Try plotting with PlotRange -> All.
The solution uses complex numbers, but its values are real and correct: sol1 = DSolveValue[{eq, i == i0}, i, t] FullSimplify[{eq, i == i0} /. i -> sol1] Block[{\[Gamma] = 1, \[Mu] = 1, \[Lambda] = 1, i0 = 1}, ...
I would use Piecewise: f[x_] := Piecewise[{{40 - 6 x, 0 Axis] Plot[f[x], {x, 0, 10}, Exclusions -> Automatic, ExclusionsStyle -> Directive[Red, Dashed]] Show[%, %%] Curiously, I could not combine Exclusions with...