Two identical uniform poles of mass 50 kg and linear mass density 15 kg/m are supported by pivots 2 m apart on level ground. At their tops are attached a wire of mass 1 kg that is stretched horizontally as shown. You may neglect any sag in the wire due to its weight. If the speed of waves that propagate along the wire is 35 m/s, what angle do the poles make with the vertical?