JEE Main & Advanced Sample Paper JEE Main - Mock Test - 35

  • question_answer
    The straight line passing through \[P({{x}_{1}},{{y}_{1}})\] and making an angle \[\alpha \] with x-axis intersects \[Ax+By+C=0\]in Q. Then PQ =

    A) \[\frac{|A{{x}_{1}}+B{{y}_{1}}+C|}{\sqrt{{{A}^{2}}+{{B}^{2}}}}\]

    B) \[\frac{|A{{x}_{1}}+B{{y}_{1}}+C|}{\sqrt{A\,\sin \alpha +B\,cos\alpha }}\]

    C) \[\frac{|A{{x}_{1}}+B{{y}_{1}}+C|}{|A\,\cos \alpha +B\,sin\alpha |}\]          

    D) \[\frac{|A{{x}_{1}}+B{{y}_{1}}+C|}{\sqrt{{{A}^{2}}{{\cos }^{2}}\alpha +{{B}^{2}}{{\sin }^{2}}\alpha }}\]

    Correct Answer: C

    Solution :

    [c]   Line is passing through the point \[P({{x}_{1}},{{y}_{1}})\] and making an angle a with x-axis. One of the points on this line at distance 'r' from the point P is given by\[({{x}_{1}}+r\cos \alpha ,\,{{y}_{1}}+r\sin \alpha )\]. If this point is Q then it lies on the line \[A({{x}_{1}}+r\cos \alpha )+B({{y}_{1}}+r\sin \alpha )+C=0.\] $\therefore \,\,\,\,r=\frac{|A{{x}_{1}}+B{{y}_{1}}+C|}{|A\cos \alpha +B\sin \alpha |}$


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