(1) proves that no matter where point P moves on AB, there is △ adq △ abq;

(2) When point P moves to any position on AB, the area of △ADQ is the area of ABCD square;

(3) If point P moves from point A to point B, and then continues to move to point C on BC, in the whole moving process, when point P moves to what position, △ADQ is just an isosceles triangle.