Medium MCQ +4 / -1 PYQ · JEE Mains 2022

If the angle made by the tangent at the point (x0, y0) on the curve $x = 12(t + \sin t\cos t)$, $y = 12{(1 + \sin t)^2}$, $0 < t < {\pi \over 2}$, with the positive x-axis is ${\pi \over 3}$, then y0 is equal to:

  1. A $6\left( {3 + 2\sqrt 2 } \right)$
  2. B $3\left( {7 + 4\sqrt 3 } \right)$
  3. C 27 Correct answer
  4. D 48

Solution

<p>$\because$ $${{dy} \over {dx}} = {{24(1 + \sin t)\cos t} \over {12(1 + \cos 2t)}} = {{1 + \sin t} \over {\cos t}} = \tan \left( {{\pi \over 4} + {t \over 2}} \right)$$</p> <p>$\because$ $${{dy} \over {d{x_{({x_0},{y_0})}}}} = \sqrt 3 = \tan \left( {{\pi \over 4} + {t \over 2}} \right)$$</p> <p>$\Rightarrow t = {\pi \over 6}$</p> <p>So, $${y_{0\left( {at\,t = {\pi \over 6}} \right)}} = 12{\left( {1 + \sin {\pi \over 6}} \right)^2} = 27$$</p>

About this question

Subject: Mathematics · Chapter: Application of Derivatives · Topic: Tangents and Normals

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