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Using multiple solutions from equations in further calculations


First: This question is a follow-up question to my question here.


Consider the following code with output:


ClearAll[a1, b1, a2, b2, xC1, yC1, xC2, yC2, c, m]
a1 := 2
b1 := 1
a2 := 1
b2 := 1/2
xC1 := 0
yC1 := 1

xC2 := 0
yC2 := 4

eqn1 = a1 (a1^2 b2^2 m^2 + b1^2 (b2^2 - (c + m xC1 - yC1)^2)) == 
       b2 (a1^2 (a2^2 m^2 + b2^2) - a2^2 (c + m xC2 - yC2)^2);
eqn2 = (a1^2 m (c - yC1) - b1^2 xC1)^2 ==
       (a1^2 m^2 + b1^2) (b1^2 xC1^2 + a1^2 (c - yC1)^2 - a1^2 b2^2);
Solve[eqn1 && eqn2, {c, m}]

{{c→−2,m→−√352},{c→−2,m→√352},{c→2,m→−√32},{c→2,m→√32}}



I need to calculate the values of the two expressions


(a1^2 m (c - yC1) - b1^2 xC1)/(a1^2 m^2 + b1^2)
(a2^2 m (c - yC2) - b2^2 xC2)/(a2^2 m^2 + b2^2)

for all four combinations of c and m. (This gives eight output values.)


Furthermore, I would like the eight output values to be named x1 to x8.


How do I do that?



Answer



ClearAll[a1, b1, a2, b2, xC1, yC1, xC2, yC2, c, m]
a1 = 2;

b1 = 1;
a2 = 1;
b2 = 1/2;
xC1 = 0;
yC1 = 1;
xC2 = 0;
yC2 = 4;

eqn1 = a1 (a1^2 b2^2 m^2 + b1^2 (b2^2 - (c + m xC1 - yC1)^2)) == 
   b2 (a1^2 (a2^2 m^2 + b2^2) - a2^2 (c + m xC2 - yC2)^2);

eqn2 = (a1^2 m (c - yC1) - b1^2 xC1)^2 == (a1^2 m^2 + b1^2) (b1^2 xC1^2 + 
      a1^2 (c - yC1)^2 - a1^2 b2^2);

sol = Solve[eqn1 && eqn2, {c, m}];

Clear[x]

Using an indexed variable and depending on the order of the sequencing desired, use either


Evaluate[Array[x, 8]] = {(a1^2 m (c - yC1) - b1^2 xC1)/(a1^2 m^2 + b1^2),
     (a2^2 m (c - yC2) - b2^2 xC2)/(a2^2 m^2 + b2^2)} /. sol // Flatten;


x /@ Range[8]

(*  {Sqrt[35]/6, Sqrt[35]/3, -(Sqrt[35]/6), -(Sqrt[35]/3), -(Sqrt[3]/
  2), Sqrt[3], Sqrt[3]/2, -Sqrt[3]}  *)

or


Clear[x]

Evaluate[Array[x, 8]] = {(a1^2 m (c - yC1) - b1^2 xC1)/(a1^2 m^2 + b1^2),

      (a2^2 m (c - yC2) - b2^2 xC2)/(a2^2 m^2 + b2^2)} /. sol // Transpose // 
   Flatten;

x /@ Range[8]

(*  {Sqrt[35]/6, -(Sqrt[35]/6), -(Sqrt[3]/2), Sqrt[3]/2, Sqrt[35]/3, -(Sqrt[35]/
  3), Sqrt[3], -Sqrt[3]}  *)

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