On the illumination of 1-symmetric convex bodies

In "Illumination of convex bodies with many symmetries", Mathematika 63 (2017), Tikhomirov verified the Hadwiger-Boltyanski Illumination Conjecture for the class of 1-symmetric convex bodies of sufficiently large dimension. We propose an alternative approach which allows us to settle the conjecture for this class in all dimensions in a uniform way. We also demonstrate that an alternative approach was indeed needed for the low dimensions. Finally, with this alternative method it is possible to solely use illuminating sets which consist of pairs of opposite directions; we thus also answer a question by Lassak, who has suggested this may be possible for any origin-symmetric convex body. As a consequence of this, we can also confirm the X-ray conjecture by Bezdek and Zamfirescu for all 1-symmetric convex bodies.