NTA Abhyas JEE Main2020MathematicsParabolaPractice
The locus of mid-points of all chords of parabola y 2 = 4 x , for which all circles drawn taking them as diameters passes through the vertex of the parabola is a conic whose length of the smallest focal chord is equal to
Options
- A1 units
- B2 units
- C3 units
- D4 units
Correct answer
B. 2 units
Step-by-step solution
Circle drawn by taking A B as diameter passes through vertex hence A V is perpendicular to B V Let h , k be the mid-point of the chord ⇒ t 1 t 2 = - 4 ,   h = t 1 2 + t 2 2 2 ,   k = 2 t 1 + t 2 2 k 2 = t 1 2 + t 2 2 + 2 t 1 t 2 ⇒ y 2 = 2 x - 8 Hence, the locus of the conic is y 2 = 2 x - 4 ⇒ Length of the latus rectum (smallest focal chord) = 2 units