BesselI[1, Sqrt[E^(2 x1) s]/Sqrt[DY]] BesselK[0, Sqrt[E^(2 r1) s]/
Sqrt[DY]] +
BesselI[0, Sqrt[E^(2 r1) s]/Sqrt[DY]] BesselK[1, Sqrt[E^(2 x1) s]/
Sqrt[DY]]
BesselI[1, Sqrt[E^(2 x1) s]/Sqrt[DY]] BesselK[0, Sqrt[E^(2 r1) s]/
Sqrt[DY]] +
BesselI[0, Sqrt[E^(2 r1) s]/Sqrt[DY]] BesselK[1, Sqrt[E^(2 x1) s]/
Sqrt[DY]]
Would you like to tell me how to multiply BesselI with BesselK? Thanks.