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 ...

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.

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.

One way to draw a Reuleaux triangle is to start with an equilateral triangle, which has three sides of equal length.

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.