English: |9/4| (isotoxal star simple 18-gon) fitting {9/4} (regular star 9/4-gon) outline.

Possible coordinates for outer vertices:
R·(cos(k2π/9+π/2);sin(k2π/9+π/2)) where R = outer radius and k ∈ {0,...,8}.
Examples: «head»: k = 0; left «foot»: k = 4; right «foot»: k = 5.

Corresponding coordinates for inner vertices:
2·sin(π/18)·R·(cos(k2π/9+11π/18);sin(k2π/9+11π/18)) where k ∈ {0,...,8}; 2·sin(π/18)·R = inner radius.

|9/4| and 9 equilateral triangles (between its 9 points) tile a regular simple 9-gon.

|9/4| is not the File:Bahai star.svg, whose points are slightly shorter.