{"action":"opened","issue":{"url":"https://api.github.com/repos/sympy/sympy/issues/9204","labels_url":"https://api.github.com/repos/sympy/sympy/issues/9204/labels{/name}","comments_url":"https://api.github.com/repos/sympy/sympy/issues/9204/comments","events_url":"https://api.github.com/repos/sympy/sympy/issues/9204/events","html_url":"https://github.com/sympy/sympy/issues/9204","id":64495574,"number":9204,"title":"dsolve fails","user":{"login":"rmairess","id":11662536,"avatar_url":"https://avatars.githubusercontent.com/u/11662536?v=3","gravatar_id":"","url":"https://api.github.com/users/rmairess","html_url":"https://github.com/rmairess","followers_url":"https://api.github.com/users/rmairess/followers","following_url":"https://api.github.com/users/rmairess/following{/other_user}","gists_url":"https://api.github.com/users/rmairess/gists{/gist_id}","starred_url":"https://api.github.com/users/rmairess/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rmairess/subscriptions","organizations_url":"https://api.github.com/users/rmairess/orgs","repos_url":"https://api.github.com/users/rmairess/repos","events_url":"https://api.github.com/users/rmairess/events{/privacy}","received_events_url":"https://api.github.com/users/rmairess/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-03-26T10:54:22Z","updated_at":"2015-03-26T10:54:22Z","closed_at":null,"body":"Dear Sir,\r\nI am using Python 3.4 and SymPy 0.7.6\r\n\r\nWhen I use the following script:\r\n\r\n# -*- coding: utf-8 -*-\r\n\r\nfrom sympy import *\r\n\r\nm = Symbol(\"m\", real=True)\r\nq = Symbol(\"q\", real=True)\r\nt = Symbol(\"t\", real=True)\r\n\r\ne1, e2, e3 = symbols(\"e1:4\", real=True)\r\nb1, b2, b3 = symbols(\"b1:4\", real=True)\r\nv1, v2, v3 = symbols(\"v1:4\", cls = Function, real=True)\r\nV1, V2, V3 = symbols(\"V1:4\", real=True)\r\nx1, x2, x3 = symbols(\"x1:4\", cls = Function, real=True)\r\n\r\nEl = Matrix([e1, e2, e3], real=True)\r\nB = Matrix([b1, b2, b3], real=True)\r\nV = Matrix([v1(t), v2(t), v3(t)], real=True)\r\nA = Matrix([Derivative(v1(t),t),Derivative(v2(t),t),Derivative(v3(t),t)], real=True)\r\n\r\n# Force de Lorentz:\r\nF = m*A -q*El -q*V.cross(B)\r\n\r\n#Système d'équations différentielles ordinaires:\r\n\r\nsol = dsolve((F[0],F[1],F[2]))\r\n\r\nfor i,s in enumerate(sol):\r\n    sol[i] = s.expand()\r\n    print(sol[i])\r\n\r\nThe solution is:\r\nv1(t) == C0*b1*q/m + C1*b1*b2*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/(b3*m) + C1*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2)*cos(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2)) + C2*b2**2*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/(b3*m) + C2*b3*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/m\r\nv2(t) == C0*b2*q/m - C1*b1**2*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/(b3*m) - C1*b3*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/m - C2*b1*b2*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/(b3*m) + C2*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2)*cos(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))\r\nv3(t) == C0*b3*q/m - C1*b1*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2)*cos(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/b3 + C1*b2*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/m - C2*b1*q*sin(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/m - C2*b2*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2)*cos(t*sqrt(b1**2*q**2/m**2 + b2**2*q**2/m**2 + b3**2*q**2/m**2))/b3\r\n\r\nBut all the e1, e2 and e3 are not there, the solution is wrong.\r\n\r\nIf I reduce the problem setting:\r\nEl = Matrix([0, 0, e3], real=True)\r\nB = Matrix([0, 0, b3], real=True)\r\nthe third equation of the system (F[2]) becomes independent of v1(t) and v2(t). But the solution is wrong. If I put sol = dsolve((F[2],F[1],F[0])) in place of sol = dsolve((F[0],F[1],F[2])), to submit the third equation in this reduced problem, the solution leads to \"False\" in sol[0]\r\nIf I solve this third equation alone, the solution is correct.\r\n\r\nThank you very much.\r\nRichard\r\n"}}