MathDB

155 birds

P_1, \ldots, P_{155}

are sitting down on the boundary of a circle

C.

Two birds

P_i, P_j

are mutually visible if the angle at centre

m(\cdot)

of their positions

m(P_iP_j) \leq 10^{\circ}.

Find the smallest number of mutually visible pairs of birds, i.e. minimal set of pairs

\{x,y\}

of mutually visible pairs of birds with

x,y \in \{P_1, \ldots, P_{155}\}.

One assumes that a position (point) on

C

can be occupied simultaneously by several birds, e.g. all possible birds.

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