In the plane rectangular coordinate system, the center of the ellipse is at the origin of the coordinate, its focus is on the X axis, and its fixed point is on the straight line x + 2y-2 = 0 In the plane rectangular coordinate system, the center of the ellipse is at the coordinate origin, its focus is on the X axis, and its fixed point is on the straight line x + 2y-2 = 0. (1) find the standard equation of the ellipse. (2) the intersection ellipse of the straight line passing through the coordinate origin o is at two points B and C, f is the left focus of the ellipse, and find the maximum area of the triangle FBC
(1)
X+2Y-2=0
Intersection with X-axis (2,0) and y-axis (0,1)
Ellipse a = 2 b = 1
The solution is x ^ 2 / 4 + y ^ 2 / 1 = 1
(2)
C = sqrt (a ^ 2-B ^ 2) = sqrt (3) (square root)
S = FO * h = sqrt(3) * b = sqrt(3)
Given the ellipse X & # 178; + 2Y & # 178; = 4, find the length of the chord with P (1,1) as the midpoint
Let y = kx-k + 1 be taken into x ^ 2 + 2Y ^ 2 = 4 to get (1 + 2K ^ 2) x ^ 2-4k (k-1) x + 2K ^ 2-4k-2 = 0, so X1 + x2 = (4K (k-1)) / (1 + 2K ^ 2) because (1,1) is the midpoint, so (x1 + x2) / 2 = 1, the solution is k = - 1 / 2 (x1-x2) ^ 2 = (x1 + x2) ^ 2-4 * X1 * x2 = 8 / 3lx1-x2l = 2 √ 6 /
Given the ellipse x square + 2Y square = 4, then the linear equation of the chord with (1,1) as the midpoint is?
The ellipse x ^ 2 + 2Y ^ 2 = 4 is known,
Let the chord circle with (1,1) as the midpoint be
A(x1,y1),B(x2,y2)
Then X1 ^ 2 + 2y1 ^ 2 = 4. (1)
x2^2+2y2^2=4.(2)
(1)-(2)
(x1^2-x2^2)+2[y1^2-y2^2]=0
(x1+x2)(x1-x2)=-2(y1+y2)(y1-y2)
The intersection circle of chords with (1,1) as the midpoint
(x1+x2)/2=1
(y1+y2)/2=1
x1+x2=2.y1+y2=2
Then (y1-y2) / (x1-x2) = - 2
That is, the slope of the straight line is - 2
And over (1,1)
Then Y-1 = - 2 (x-1)
2x+y-3=0
Given the ellipse X & # 178; + 2Y & # 178; = 4, then the length of the chord with (1,1) as the midpoint is
Intersection (x1, Y1) (X2, Y2) X1 + x2 = 2, Y1 + y2 = 2, chord length is √ (x1-x2) ^ 2 + (y1-y2) ^ 2 = √ (1 + K ^ 2) | x1-x2 | K is the slope of straight line X1 & # 178; + 2y1 & # 178; = 4x2 & # 178; + 2Y2 & # 178; = 4, subtracting to get: (y1-y2) / (x1-x2) = - 1 / 2 (x1 + x2) / (Y1 + Y2) = - 1 / 2, the slope of straight line is - 1 / 2