Question about the minor and major axes' length formulas

[Steven]

Hello, I have a question about the elliptical features minor and major axes’ length. The formulas given in the Pyradiomics documentation are respectively 4sqrt(lambda_major) and 4sqrt(lambda_minor), with lambda_major and lambda_minor being the largest and smallest principal components of the physical coordinates of the pixels to which the ellipse is fitted. I was wondering if a demonstration of these formulae was available somewhere as I did not manage to find it. Thanks in advance!