(2)AE=t OE=2-t,BD= 2t,AD = 4-2t;
If AEFD is a diamond,
t=4-2t,
t=4/3
(3) If PA=PC, then P(2 3,0);
If AP=AC, then P(2 7,0) P (-2 7,0);
If PC=AC, then P(2 3+2-2 5,0).