(1) Given that point O is any point on the plane of equilateral triangle ABC, connect OA and extend to e such that AE = OA with OB.OC Make a parallelogram obfc for the adjacent edge and connect EF. Please explore the quantitative relationship between EF and BC. (2) Given that point O is any point on the plane of the isosceles right triangle ABC (BC is the hypotenuse), connect OA and extend to e, so that AE = OA. Take ob.oc as the adjacent side, make a parallelogram obfc, connect EF. Then the quantitative relationship between EF and BC is () (3) given that point O is any point on the plane of right triangle ABC (BC is the hypotenuse), connect OA and extend it to e, so that AE = OA, and connect EF with OB and OC as parallelogram obfc. Please explore the quantitative relationship between EF and BC.

(1) Given that point O is any point on the plane of equilateral triangle ABC, connect OA and extend to e such that AE = OA with OB.OC Make a parallelogram obfc for the adjacent edge and connect EF. Please explore the quantitative relationship between EF and BC. (2) Given that point O is any point on the plane of the isosceles right triangle ABC (BC is the hypotenuse), connect OA and extend to e, so that AE = OA. Take ob.oc as the adjacent side, make a parallelogram obfc, connect EF. Then the quantitative relationship between EF and BC is () (3) given that point O is any point on the plane of right triangle ABC (BC is the hypotenuse), connect OA and extend it to e, so that AE = OA, and connect EF with OB and OC as parallelogram obfc. Please explore the quantitative relationship between EF and BC.

(1) Note that the diagonal intersection of the parallelogram obfc is m, then BM = MC, OM = MF; when connecting am, because △ ABC is an equilateral triangle, am = √ 3bC / 2, and in △ AEF, am is the median line, so EF = 2am, EF = √ 3bC
(2) The results show that EF = 2am = BC
(3) (2), EF = BC