In cone-beam tomography Differentiated BackProjection method (DBP) is a suitable approach for image reconstruction from truncated projections. However, the reconstruction of a point with this method is possible only if the point lies on a chord connecting two source positions of the x-ray source trajectory. Using an approach initially proposed for the reverse helix with axial truncation, we present a configuration and its associated (theoretical) reconstruction method to deal with points which do not lie on any chord of the 3-sin trajectory (sine on a cylinder of period 2π/3) and with transversely truncated projections.