JEE Mains · Maths · STD 11 - 10.2 parabola,ellipse,hyperbola
Let \(x=2 t, y=\frac{i}{3}\) be a conic. Let \(S\) be the focus and \(B\) be the point on the axis of the conic such that \(SA \perp BA\), where \(A\) is any point on the conic. If \(k\) is the ordinate of the centroid of \(\Delta SAB\), then \(\lim _{ t \rightarrow 1} k\) is equal to
- A \(\frac{17}{18}\)
- B \(\frac{19}{18}\)
- C \(\frac{11}{18}\)
- D \(\frac{13}{18}\)
Answer & Solution
Correct Answer
(D) \(\frac{13}{18}\)
Step-by-step Solution
Detailed explanation
parabola \(x ^{2}=12 y\) \(SA \perp SB\) so, \(m _{ AS } \cdot m _{ AB }=-1\) \(\frac{\left(3-\frac{ t ^{2}}{3}\right)}{(0-2 t )} \cdot \frac{\left(\alpha-\frac{ t ^{2}}{3}\right)}{(0-2 t )}=-1\) by solving \(3 \alpha=\frac{27 t^{2}+t^{4}}{t^{2}-9}\) ordinate of centriod of…
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