These are all complex solutions. There might be more if we take ArcSin
and ArcCos
as multi-functionsmultivalued functions.
sol = {9/5 - (2 I Sqrt[11])/5,
1/5 - (2 I)/5, -1, -3 - (2 I)/Sqrt[5], -(23/5) - (2 I Sqrt[19])/5,
9/5 + (2 I Sqrt[11])/5,
1/5 + (2 I)/5, -(9/5), -3 + (2 I)/Sqrt[5], -(23/5) + (
2 I Sqrt[19])/5};
With[{x = a + I b},
ContourPlot[{Re[2 ArcCos[Sin[Pi*x]] - Pi*Cos[ArcSin[x + 1]]] == 0,
Im[2 ArcCos[Sin[Pi*x]] - Pi*Cos[ArcSin[x + 1]]] == 0}, {a, -10,
10}, {b, -4, 4}, PlotPoints -> 100, Epilog -> Point@(ReIm /@ sol)]]