A parabola V whose focus is s(0,0) and passing through P (3,4). Equati...
Given Information:
- Focus of parabola V is s(0,0).
- Parabola V passes through point P(3,4).
- Equation of tangent at P to parabola V is 3x + 4y - 25 = 0.
- A chord through S parallel to tangent at P intersects the parabola at A and B.
To Find:
Which of the following statements are correct?
- Length of AB is 20 units.
- Latus rectum of parabola is 20 units.
- Only one real normal can be drawn from the point (-3,-4).
- Only one real normal can be drawn from the point (-6,-8).
Solution:
Step 1: Find the equation of parabola V
As the focus of parabola V is s(0,0), the equation of parabola can be written as x² = 4ay.
Let P be a point on the parabola V. Hence, (3,4) lies on the parabola.
Substituting the coordinates of point P in the equation of parabola, we get:
3² = 4a(4)
a = 9/16
Therefore, the equation of parabola V is x² = (9/4)y.
Step 2: Find the coordinates of point S
As the focus of parabola V is s(0,0), the coordinates of point S are (0,1/a).
Substituting the value of a, we get S(0,16/9).
Step 3: Find the coordinates of points A and B
As chord AB is parallel to tangent at P, the slope of AB is equal to the slope of tangent at P.
Slope of tangent at P is (-3/4).
Let the coordinates of point A be (h, k). As point A lies on the parabola V, we have h² = (9/4)k.
As chord AB is parallel to tangent at P, the coordinates of point B can be written as (h + 4k/3, k + 3h/4).
As chord AB passes through point S, the coordinates of point B can be written as (4k/3, k + 3h/4).
As chord AB is a part of parabola V, the coordinates of point B can be written as [(9/4)k + 4k/3, k + 3(9/4)k/4].
Solving the above equations, we get h = 3, k = 27/4.
Therefore, the coordinates of points A and B are A(3, 27/4) and B(4, 9).
Step 4: Check the given statements
- Length of AB is 20 units.
Using distance formula, we find