Intersection of one sector (r, θ₁, θ₂) of the transmittance grid (boundaries in blue) with the star (boundaries in yellow). The intersection area can be subdivided into the sum of circular segments (yellow when the circle is the star; blue when the circle is the planet) and triangles (subparts of A₀, in red). Here, the maximum number of intersections has been displayed. Fig. A.3 shows examples of cases with fewer intersections.