JEE Main & Advanced Mathematics Straight Line Question Bank Slope of line, Equation of line in different forms

  • question_answer
    The line passing through \[(-1,\pi /2)\] and perpendicular to \[\sqrt{3}\sin \theta +2\cos \theta =\frac{4}{r}\] is                                     [EAMCET 2003]

    A)            \[2=\sqrt{3}\,r\cos \theta -2\,r\sin \theta \]                                

    B)            \[5=-2\sqrt{3}\,r\sin \theta +4\,r\cos \theta \]

    C)            \[2=\sqrt{3}\,r\cos \theta +2\,r\cos \theta \]

    D)            \[5=2\sqrt{3}\,r\sin \theta +4\,r\cos \theta \]                            

    Correct Answer: A

    Solution :

               Perpendicular to \[\sqrt{3}\sin \theta +2\cos \theta =\frac{4}{r}\] is                    \[\sqrt{3}\sin \left( \frac{\pi }{2}+\theta  \right)+2\cos \left( \frac{\pi }{2}+\theta  \right)=\frac{k}{r}\]                    It is passing through \[(-1,\,\pi \,/\,2)\]                  \[\sqrt{3}\sin \pi +2\cos \pi =\frac{k}{-1}\Rightarrow k=2\]                    \ \[\sqrt{3}\cos \theta -2\sin \theta =\frac{2}{r}\]Þ \[2=\sqrt{3}r\cos \theta -2r\sin \theta \].


You need to login to perform this action.
You will be redirected in 3 sec spinner