② If the analytical formula of straight line AB is y=kx+2, the midpoint n coordinate of CD can be calculated as (2k, 0); if the analytical formula of straight line CF is y=k'x+2, it can be substituted into the point n coordinate to calculate k×k'=- 1, and the straight line AB is perpendicular to the straight line CF, and the tangent can be obtained;

(2) Let the analytical formula of the rotated straight line AB be y = k "x+2, and find out the abscissa of A and B (by the formula method of solving the quadratic equation of one variable), so that the coordinates of C and D can be obtained, and then the coordinates of P can be calculated, so that K" can be used to represent PC (the abscissa of C minus the abscissa of P) and PD (the abscissa of D minus P).

(because the root number is not easy to play, so I can only talk about ideas. I did a rough calculation, but I didn't look it up. K'' = 1, I don't know if it's right. )