If the difference between the distance from the moving point P (x, y) (Y > 0) to the point F (0,2) in the plane and the distance to the X axis is 2, then the trajectory equation of the moving point P is_______ ．

If the difference between the distance from the moving point P (x, y) (Y > 0) to the point F (0,2) in the plane and the distance to the X axis is 2, then the trajectory equation of the moving point P is_______ ．

[√x²＋﹙y－2﹚² ] ﹣|y| =±2
y＞0
[√x²＋﹙y－2﹚² ]=y±2
X & # 178; + Y & # 178; - 4Y + 4 = y & # 178; + 4Y + 4 or X & # 178; + Y & # 178; - 4Y + 4 = y & # 178; - 4Y + 4
X & # 178; = 8y or x = 0
y=1/8x² x=0

It is known that the circle O: x2 + y2 = 5 and the straight line L: xcos θ + ysin θ = 1 (0 ＜θ＜π 2). Let K be the number of points on the circle O whose distance from the straight line L is equal to 1, then K=______ ．

From the equation of circle, we can get the following results: Center o (0,0), radius r = 5, distance d = 1cos2 θ + sin2 θ = 1 ＜ 5, and R-D = 5-1 ＞ 1 = D, the number of points on circle O whose distance to line L is equal to 1 is 4, that is k = 4