Can/Will you post a sketch of what you have in mind.
I learned, the hard way, that the triangle in a square unit has different angles that 30-60-90 and 60-60-60!
Attached is a drawing of the triangle in a square unit with the angles to the nearest thousandth of a degree.
360 divided by 7 equals 51.429 degrees, so the Tri-Recs ruler is not appropriate for a circle evenly divided by 7. The "center angle" of the larger ruler is approximately 53.130 degrees, which multiplied by 7 equals approximately 371.910 degrees.