The Y axis cuts the equilateral triangle into two 30/60 degree right triangles..........................so with the triangle at the left..................is the 30/60 right triangle..................made by the Y axis...........the Y and X axis form 4 right angles............they run perpendicular to each other.......................to I know the hyp is one........................from - 1/2 to 1/2 is a distance of 1..................one half plus one half equals one.........................two half dollars is a dollar........................

So the bottom has to be 0.5...............1/2............on the triangle at left............why?  It is the distance from the origin to (1/2, 0)...........................zero to one half.........is a distance of one half...........