Therefore, ............................................. 1 min.
The solution is ................................................................. 1 min.
The analytical formula of parabola is .................................... 1.
(2) Point B is perpendicular to the axis, the vertical foot is H, Point A is AG⊥BO, and the vertical foot is G.
∫a(0， 1)，B (4，3)，∴ OA = 1，OB = 5 .............................................................................................................
* ∴ ∴ Joint-stock company = ...1point
∴∴ og = BG = ...........................................................1min.
∴ Tan ∠ ABO = .................................................1min.
(3)∵ Let the analytical formula of straight line AB be
Substitute a (0, 1) and b (4 4,3) to get the solution.
∴ The analytical formula of straight line AB is ................................................. 1 min.
Let m, n, Mn =................ 1 min.
∫ Quadrilateral MNCB is a parallelogram, ∴=3. ∴mn=bc=3.
The solution is ..................................................................... 1 min.
The parabola symmetry axis is a straight line, and the straight line MN is on the left side of the parabola symmetry axis.
..................... 1 point
∴∴ .............................................................................................................................+0 points.
25. Solution: (1) In Rt△ABC, ∠ BAC = 90, ∠ ABC = 60, AB = 4,
∴ ............................................1min.
From folding to ∠ Abd = 30, we get ... 0.
∴ CD = .................................................1min.
② From folding ∠ bed = ∠ bad = 90, ∴∠ced = 90°, ∴∠CED=∠CAB.
And ∫∠DCE =∠DCE, ∴△ CED ∽△ cab .................................................1min.
∴,∵,∴,∵
............................................... 1 min.
DE = AD = y, ..................................................... 1 min.
∴ ................................................... 2 points.
(3) the intersection point c is CH⊥BG and the vertical foot is H.
∵bg∥ac,∴∠acb=∠cbg,∵∠acb=∠cgb,∴∠cbg=∠cgb，
∴ CB = CG- 1。
∴BH=HG=AC=x, ∴BG=2x, ................................................ 1 min.
∵AE⊥BD,∴∠ADB+∠DAE=∠DAE+∠BAG=90，
∴∠ ADB = ∠ bag ............................................. 1 min.
∠∠BAC =∠ABG = 90，△ Abd ∽△ BGA。
∴ ............................................1min.
∴∴ ..................................................................................1min.
∵,
∴, solution (negative value has been abandoned)
That is AC = ..........................................................1min.