It is shown that in any polygonal art gallery of n sides it is possible to place ⌊n/3⌋ point guards whose range of vision is 180° so that every interior point of the gallery can be seen by at least one of them. The guards can be stationed at any point of the art gallery. This settles an open problem posed by J. Urrutia. © 2000 Elsevier Science B.V.
Tóth, C. D. (2000). Art gallery problem with guards whose range of vision is 180. Computational Geometry: Theory and Applications, 17(3–4), 121–134. https://doi.org/10.1016/S0925-7721(00)00023-7