Plot[{BesselY[1,x],BesselJ[1,x]},{x,0,5}]

Plot[{BesselJ[0,x],BesselJ[1,x]},{x,0,5}]

FindRoot[BesselJ[1,x]== 0,{x,4}]

Evaluate[D[BesselJ[0,x],x]]

N[BesselJ[0,3.831705970207512`]]