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:
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
This question is part of PrepWiser's free JEE Main question bank. 99 more solved questions on Application of Derivatives are available — start with the harder ones if your accuracy is >70%.