As shown in the figure, the circle C: (x-1) 2 + y2 = R2 (R & gt; 1) Let m be the intersection of the circle C and the negative half axis of the x-axis, and let m be the chord Mn of the circle C passing through M, and let its midpoint P just fall on the y-axis. (I) when r = 2, find the coordinates of the point P satisfying the condition; (II) when R ∈ (1, + ∞), find the equation of the locus g of point n; (III) the line L passing through point P (0,2) intersects with the locus g in (II) at two different points E and F, if CE · CF & gt; 0, find the value range of the slope of the line L

As shown in the figure, the circle C: (x-1) 2 + y2 = R2 (R & gt; 1) Let m be the intersection of the circle C and the negative half axis of the x-axis, and let m be the chord Mn of the circle C passing through M, and let its midpoint P just fall on the y-axis. (I) when r = 2, find the coordinates of the point P satisfying the condition; (II) when R ∈ (1, + ∞), find the equation of the locus g of point n; (III) the line L passing through point P (0,2) intersects with the locus g in (II) at two different points E and F, if CE · CF & gt; 0, find the value range of the slope of the line L

(1) Let n (x, y) be known, then (x-1) 2 + y2 = 4x-1 = 0, then n (1, ± 2) is obtained. So the coordinates of the midpoint P of Mn are (0, ± 1). (2): let n (x, y) be known, and let y = 0 in the circular equation, then the coordinates of m point are (1-r, 0). Let P (0, b) be obtained by kcpkmp = - 1 (or by Pythagorean theorem): r = B2 + 1 Then (x-1) 2 + y2 = r2x + 1-r = 0, eliminate R and R & gt; 1, so the trajectory equation of point n is y2 = 4x (x ≠ 0). (3) let the equation of line l be y = KX + 2, m (x1, Y1), n (X2, Y2), y = KX + 2Y2 = 4x, eliminate y to get k2x2 + (4k-4) x + 4 = 0, because line L and parabola y2 = 4x (X & gt; 0) intersect at two different points m, N, so △ = - 32K + 16 & gt; 0, so K & lt; 12, and because cm · CN & gt; 0, so (x1-1) (x2-1) + y1y2 & gt; 0, so (K2 + 1) x1x2 + (2k-1) (x1 + x2) + 5 & gt; 0, K2 + 12K & gt; 0, so K & gt; 0 or K & lt; - 12. In conclusion, 0 & lt; K & lt; 12 or K & lt; - 12 can be obtained