So I have this expression
Expr= (5.70129*10^14 f^2 (7.97764*10^8 + 4 f^2 \[Pi]^2) +
6198.06 (-6.34731*10^8 + 4 f^2 \[Pi]^2)^2 (7.97764*10^8 +
4 f^2 \[Pi]^2) +
13149.6 (6.34731*10^8 + 4 f^2 \[Pi]^2) (3.14945*10^10 f^2 +
0.648892 (-7.97764*10^8 +
4 f^2 \[Pi]^2)^2))/((3.14945*10^10 f^2 +
0.648892 (-7.97764*10^8 + 4 f^2 \[Pi]^2)^2) (2.50582*10^10 f^2 +
0.272416 (-6.34731*10^8 + 4 f^2 \[Pi]^2)^2))
I want to solve
Eqn = Abs[Expre - 0.00012] = 0.99*0.00012
However when I do
Eqn = Abs[Expre - 0.00012] = 0.99*0.00012
aux = Quiet[FindRoot[Eqn, {f, 3000}]];
result = f /. aux[[1]]
I obtain result = 42013.8 instead of a value around 3000 or 4000 (the correct answer).
What am I doing wrong?
Abs[Expre-0.00012]-0.99*0.00012
and see that the plot in in the negative part of the plane to the left of your solution. $\endgroup$