# Solve large equation with parameters?

Posted 3 years ago
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 I have a very large expression: j - Sqrt[q^2 + qp^2 - 2 q qp Cos[\[Theta]]] - \[Sqrt](qp^2 + 1/2 (16 m5^2 + ma^2 + mp^2 - Sqrt[(-(16 m5^2) - ma^2 - mp^2)^2 - 4 (ma^2 mp^2 - 16 m5^2 qp^2)])) == 0 where \[Theta] = Pi/6; ma = 980; mp = 139; j = \[Sqrt](q^2 + 1/2 (16 m5^2 + ma^2 + mp^2 + Sqrt[(-(16 m5^2) - ma^2 - mp^2)^2 - 4 (ma^2 mp^2 - 16 m5^2 q^2)])) And $qp$ is real and positive. I want to find qp as function $q>0$ and $m5>0$ (if it is imposible then function only $q>0$ and $m5=constant=100>0$). I atemted to solve this the next way: Solve[ j - Sqrt[ q^2 + qp^2 - 2 q qp Cos[\[Theta]]] - \[Sqrt](qp^2 + 1/2 (16 m5^2 + ma^2 + mp^2 - Sqrt[(-(16 m5^2) - ma^2 - mp^2)^2 - 4 (ma^2 mp^2 - 16 m5^2 qp^2)])) == 0 && qp > 0 , qp, Reals]; Mathematica hangs after two hour calculation. Where I am wrong? After calculation I want to plot function form: $z=q^2+m5^2$ (in reality this is more complicated)x-post on MSE: link