No a yield sign does not form a right triangle.
If all sides are equal, that is an equilateral triangle, where all angles are equal as well. In a triangle, there are 180 degrees. If all angles are equal in an equilateral triangle, each angle is 60. 180/3=60 In order for a triangle to be a right triangle, the triangle must have a right angle, which is 90 degrees. So equilateral triangles can NEVER be right triangles.
Hope this helped!