def ptdAngle(self,t,dangle):
        """
        NAME:

           ptdangle

        PURPOSE:

           return the probability of a given stripping time at a given angle along the stream

        INPUT:

           t - stripping time

           dangle - angle offset along the stream

        OUTPUT:

           p(td|dangle)

        HISTORY:

           2013-12-05 - Written - Bovy (IAS)

        """
        if isinstance(t,(int,float,numpy.float32,numpy.float64)):
            t= numpy.array([t])
        out= numpy.zeros(len(t))
        if t > 0.:
            dO= dangle/t[t < self._tdisrupt]
        else:
            return 0.
        #p(t|a) = \int dO p(O,t|a) = \int dO p(t|O,a) p(O|a) = \int dO delta (t-a/O)p(O|a) = O*2/a p(O|a); p(O|a) = \int dt p(a|O,t) p(O)p(t) = 1/O p(O)
        out[t < self._tdisrupt]=\
            dO**2./dangle*numpy.exp(-0.5*(dO-self._meandO)**2.\
                                         /self._sortedSigOEig[2])/\
                                         numpy.sqrt(self._sortedSigOEig[2])
        return out