In short: Let there be a right-angled triangle ABC with hypotenuse AB. Let the triangle revolve around the BC side. I would like to ask for your help to determine the angle of revolution using a revolved triangle (ABCr) with known angles (Ar, Br and Cr = C = 90°) and known lengths (ABr, BCr = BC, and ACr). (illustration of triangle and axis of revolution)
For the context, this is a question based on an orthopaedics paper which proposes the following solution to the problem: (image from the orthopaedics paper) (image illustrating what I understand that the paper suggests)
Update: I found an online simulator which demonstrates exactly what I am trying to illustrate: https://www.geogebra.org/m/eSpdvEpm check "rotate around y-axis", and rotate a bit => is it possible to determine the angle of rotation just by comparing the initial image with the rotated image?