Equilateral Triangle on Parallel Lines 平行線上的等邊三角形

Construct an equilateral triangle whose vertices (one of them is the given point A) respectively lie on three parallel lines.
畫出一等邊三角形，三個頂點(其中一頂點為A)分別位於三條平行線上。
– TLLF

Information: Equilateral Triangle on Parallel Lines 平行線上的等邊三角形