Illustration of projection effects due to WAT orientation (rotation). In panels a - f the geometry of the problem is visualized and explained step by step (follow the text of Appendix E), and in panel g the projection is analyzed for the real case - radio galaxy 10913. In all panels x-y plane corresponds to the plane of the sky, and z axis aligns with the LoS (pointing towards the observer). Markings A, P, C and R denote the radio core, the bending point, the center and the radius of the osculating circle at the bending point, respectively. P′ and C′ are the projected locations of P and C after rotation. Panel a: WAT lies entirely in the plane of the sky, R - radius of the osculating circle at the bending point, P, can be extracted directly from the observations; Panel b: WAT rotated by angle Θ around x-axis (tilted from the plane of the sky); gray indicates original jet position and osculating circle; Panel c: WAT rotated by angle ϕ around y-axis; Panel d: WAT rotated by Θ (x) and ϕ (y), projected osculating circle transformed into an ellipse; Panels e and f: Effect of Θ (e) and ϕ (f) rotations on x and y components of the projected R; Panel g: Observed radio morphology of WAT 10913, measuring projected x and y components of R.