Fishburn raised a problem that whether there exists a 4-isosceles 6-point with no 4-point on a circle and no 3-point on a line.
Fishburn提出是否存在无4点共圆、无3点共线的4等腰6元集。
Two graphical methods“four nodes on same circle”and “involute method”-for the consrtuction of complex slip line field are introdued.
介绍两种求解复杂滑移线场的图解法——四点共圆法和渐开线法，论述了求解基本原理及作图方法。