[Graphics:Images/Iso-P2_gr_1.gif]

The isosceles triangle ABC, CD = DB/2:
    two cases

1. AB = CB:
      CB = 3/4 AC, Cos[α] = 2/3.

[Graphics:Images/Iso-P2_gr_2.gif]

2. AC = CB:
      CB = 3/2 AB,  Cos[α] = 1/3.

[Graphics:Images/Iso-P2_gr_3.gif]

Converted by Mathematica      December 28, 2001