Triangles and elliptic curves. IV (Q1908710)

The author continues his work on elliptic curves associated to triangles as described in part I, ibid. 70, No. 4, 106-108; part II, ibid., No. 7, 223-225; and part III, ibid., No. 10, 311-314 (1994); see respectively Zbl 0824.14028 and 14029 and Zbl 0832.14021). He proves a theorem which may be viewed as a geometric background for typical relations between elliptic curves which are quadratic twists of each other. An example is given where the field of rationality is \(\mathbb{F}_q\), \(q\) odd.