过圆内一点M任作两条弦CD、EF,连结CF、DE,就得到圆的内接蝶形CDEF.本文主要研究一直线与射线DF、CE、弦CD、EF和圆相交的情况.这与文〔1〕、〔2〕的已知条件略有差异,但其关系式却类同.定理1如图1,在圆的内接蝶形CDEF中, A circular MCD for two strings of CDs, EFs, and links to CFs and DEs is obtained by rounding a point M in the circle. This paper mainly studies the case where a straight line intersects with rays DF, CE, chord CD, EF and circle. This is a little different from the known conditions in [1] and [2], but their relations are similar. Theorem 1 As shown in Fig. 1, in a butterfly inscribed butterfly CDEF,