Isn't an equilateral triangle at 60 degrees? From what I remember from geometry, all triangle angles add up to 180, like if you had an isosceles 2 at 45, then the last one would have to be 90.
Also, there are two types of blocks for that quilt, a hexagon and an octogon, I know the hex needs a 60 degree ruler, but I don't remember what the octogon one needs.