wxMaxima 从 "solve" 中提取解决方案

Question

我有以下代码，在倒数第二条指令之前都可以正常工作。

(%i17)  M_A;

(%o17)  [500.0,-0.22*F_Bz-750.0,0.22*F_By-105.0]

(%i18)  solve(M_A[2]);

rat: replaced -750.0 by -750/1 = -750.0

rat: replaced -0.22 by -11/50 = -0.22

(%o18)  [F_Bz=-37500/11]

(%i19)  solve(M_A[3]);

rat: replaced -105.0 by -105/1 = -105.0

rat: replaced 0.22 by 11/50 = 0.22

(%o19)  [F_By=5250/11]

(%i20)  F_Br : sqrt(F_By^2+F_Bz^2);

(%o20)  sqrt(F_Bz^2+F_By^2)

(%i21)  float(%);

(%o21)  sqrt(F_Bz^2+F_By^2)

如何获得 %i20 的数字答案。

Answer 1

这是我尝试将方程的解代入 F_Br 的表达式时得到的结果。参见 %i7 和 %o7。

(%i3) M_A:[500.0,(-0.22)*F_Bz-750.0,0.22*F_By-105.0]
(%o3)   [500.0, (- 0.22 F_Bz) - 750.0, 0.22 F_By - 105.0]
(%i4) s1:solve(M_A[2])

rat: replaced -750.0 by -750/1 = -750.0

rat: replaced -0.22 by -11/50 = -0.22
                                  37500
(%o4)                   [F_Bz = - -----]
                                   11
(%i5) s2:solve(M_A[3])

rat: replaced -105.0 by -105/1 = -105.0

rat: replaced 0.22 by 11/50 = 0.22
                                  5250
(%o5)                     [F_By = ----]
                                   11
(%i6) F_Br:sqrt(F_By^2+F_Bz^2)
                                2       2
(%o6)                  sqrt(F_Bz  + F_By )
(%i7) subst(append(s1,s2),F_Br)
                         750 sqrt(2549)
(%o7)                    --------------
                               11
(%i8) float(%)
(%o8)                   3442.337880372093

wxMaxima 从 "solve" 中提取解决方案

wxMaxima extract solution from "solve"

wxmaxima