JEE Main & Advanced Mathematics Straight Line Question Bank Distance between two lines, Perpendicular distance of the line from a point Position of point w.r.t. line

  • question_answer
    The equation of the base of an equilateral triangle is \[x+y=2\] and the vertex is (2, -1). The length of the side of the triangle is [IIT 1973, 83, MP PET 1995; RPET 1999, 2000]

    A) \[\sqrt{3/2}\]                            

    B) \[\sqrt{2}\]

    C) \[\sqrt{2/3}\]                            

    D) None of these

    Correct Answer: C

    Solution :

    Let p be the length of the perpendicular from the vertex (2, ?1) to the base \[x+y=2\].                    Then \[p=\left| \frac{2-1-2}{\sqrt{{{1}^{2}}+{{1}^{2}}}} \right|=\frac{1}{\sqrt{2}}\]                    If 'a' be the length of the side of triangle, then\[p=a\sin {{60}^{o}}\Rightarrow \frac{1}{\sqrt{2}}=\frac{a\sqrt{3}}{2}\Rightarrow a=\sqrt{\frac{2}{3}}\].


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