When I first saw this unit, I also thought it was an equilateral triangle flanked by 30-60-90 degree triangles.
It isn't.
The angles are - approximately - on the skinny triangle: 26.57, 63.43 and 90 degrees
The angles on the bigger triangle are - approximately: the base angles are 63.44, 63.44, and the top angle is 53.12 degrees
The easiest way to draft this is by drawing a square, then putting in the triangle lines and adding seam allowances to the triangles.