The length of a focal chord of the parabola y^2 = 4ax at a distance b from the vertex is c. Then

JEE Advanced Mathematics question

The length of a focal chord of the parabola at a distance from the vertex is . Then

Answer: (D)

Let the focal chord make angle with the axis. It passes through , so its distance from the vertex is

b = OSθ = aθ.

Length of a focal chord inclined at : with ends , length and slope , which gives

c = 4a

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Question ID VK-109004