(20) (The full mark of this question is 15) As shown in the figure, in the rectangular ABCD, the points E and F are on the AB line and the AD line respectively, and AE=EB=AF= will be folded into a plane BEF along the straight line EF.

(i) Find the cosine value of dihedral angle;

(II) Points M and N are on lines FD and BC, respectively. If the quadrilateral MNCD is folded up along the straight line MN, C will be obtained.

Coincidence with, find the length of line FM.

(2 1) (full mark of this question 15) It is known that straight ellipses are the left and right focuses of ellipse C, respectively.

(i) When a straight line passes through the right focus F2, find the equation of the straight line;

(II) Let the straight line and ellipse c intersect at points A and B, and the centers of gravity are g and h respectively. If the origin o is in a circle with a diameter of line segment GH, the range of the number m should be found.

(22) (The full mark of this question is 14) It is known that A is a given real constant and the function is the maximum point.

(i) Find out the value range of b;

(2) Suppose there are three extreme points, and ask if there is a real number B, which can be found, so that a certain arrangement (among them) becomes arithmetic progression in turn? If yes, point out all B's and corresponding ones; if no, explain the reasons.