Polygon Side Does Note Match to Polygon rect

[hh]

A triangle with width=height is NOT a regular polygon (it doesn't have equal side length).

To have what you want create a grc of type "polygon" and then

set points of grc 1 to "0,0,10,-10,20,0,0,0"
set width of grc 1 to 243
set height of grc 1 to 243

To have equal sideLength you set the width to 243/sin(pi/3).