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WBJEE · Maths · Parabola

Let the tangent and normal at any point \(P\left(at^2\right.\), 2at), \((a > 0)\), on the parabola \(y^2=4 a x\) meet the axis of the parabola at \(T\) and \(\mathrm{G}\) respectively. Then the radius of the circle through \(\mathrm{P}, \mathrm{T}\) and \(\mathrm{G}\) is

  1. A \(a\left(1+t^2\right)\)
  2. B \(\left(1+t^2\right)\)
  3. C \(a\left(1-t^2\right)\)
  4. D \(\left(1-\mathrm{t}^2\right)\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(a\left(1+t^2\right)\)

Step-by-step Solution

Detailed explanation

\(P\left(a t^2, 2 a t\right), T\left(-a t^2, 0\right), G\left(2 a+a t^2, 0\right)\) Slope of \(P T \times\) Slope of \(P G=-1\) \(\therefore\) TG is a diameter of the circle through points \(\mathrm{P}, \mathrm{T}\) and \(\mathrm{G}\).…