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 distance of the lines \[2x-3y=4\]from the point (1, 1) measured parallel to the line \[x+y=1\] is               [Orissa JEE 2002]

    A)            \[\sqrt{2}\]                               

    B)            \[\frac{5}{\sqrt{2}}\]

    C)            \[\frac{1}{\sqrt{2}}\]                

    D)            6

    Correct Answer: A

    Solution :

               The slope of line \[x+y=1\] is \[-1\]                    \ It makes an angle of \[135{}^\circ \] with x-axis.                    The equation of line passing through \[(1,\,\,1)\] and making an angle of \[135{}^\circ \] is, \[\frac{x-1}{\cos {{135}^{o}}}=\frac{y-1}{\sin {{135}^{o}}}=r\]                    Þ \[\frac{x-1}{-1/\sqrt{2}}=\frac{y-1}{1/\sqrt{2}}=r\]                    Co-ordinates of any point on this line are \[\left( 1-\frac{r}{\sqrt{2}},1+\frac{r}{\sqrt{2}} \right)\]If this point lies on \[2x-3y=4\], then                    \[2\left( 1-\frac{r}{\sqrt{2}} \right)-3\left( 1+\frac{r}{\sqrt{2}} \right)=4\]Þ \[r=\sqrt{2}.\]


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