To represent this in two dimensions, again draw an equilateral triangle, followed by a circle centered around one of the triangle’s vertices, with a radius as long as each of the triangle’s legs.

By placing this equilateral triangle between the legs of the figure, Leonardo achieves a specific proportion in the drawing. The side of the square compared to the radius of the circle yields a ...

It could just be coincidence, but I experimented with the illustration, overlaying it with an equilateral tringle of appropriate size, and a circle centred on the triangle's apex, using MS Visio ...

Hidden triangle The paper describes a hidden detail in the Vitruvian Man, namely an equilateral triangle between the man's legs referenced in da Vinci's notes for the drawing.

Using such an equilateral triangle in the Vitruvian Man drawing helps produce a specific ratio – 1.64 – between the size of the square and the circle in the artwork.

Using such an equilateral triangle in the Vitruvian Man drawing helps produce a specific ratio – 1.64 – between the size of the square and the circle in the artwork.