Try this: 1. Create a circle with a diameter of 6 inches. 2. Create an equilateral triangle that is 5.175 inches wide. Center the two objects to the middle of a page.

Shouldn't the triangle be in the center of circle?

Edit: The workaround I have found is to use a hexagon and then when you have it in the right position, convert it to a triangle.

This is inconvenient and unintuitive.