? (1) firstly, the circle C 1 and the straight line C2 are converted into cartesian coordinate equations, then the simultaneous equations are used to solve the cartesian coordinates of their intersections, and finally they are converted into polar coordinates;

(2) From (1), we can know that the coordinates of point P and point Q are (0,2) and (1, 3) respectively, so that the rectangular coordinate equation of straight line PQ is x-y+2=0, and y=bx/2-ab/2+ 1 can be obtained from the parameter equation, thus constructing.

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