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The sides of a rhombus ABCD are parallel to the lines, x−y+2=0 and 7x−y+3=0. If the diagonals of the rhombus intersect at P(1, 2) and the vertex A (different from the origin) is on the y-axis, then the ordinate of A is :

  • Option 1) 5/2

     

  • Option 2) 7/4

     

  • Option 3) 2

     

  • Option 4) 7/2

     

 

Answers (1)

best_answer

As we learned,

 

Condition for parallel lines -

m_{1}= m_{2}

- wherein

Here m_{1},m_{2} are the slope of two lines

 

 and

 

Equation of angle bisectors -

\frac{a_{1}x+b_{1}y+c_{1}}{\sqrt{a_{1}^{2}+b_{1}^{2}}} =\frac{\pm a_{2}x+b_{2}y+c_{2}}{\sqrt{a_{2}^{2}+b_{2}^{2}}}

 

- wherein

Angle bisectors of the lines a_{1}x+b_{1}y+c_{1}=0   and a_{2}x+b_{2}y+c_{2}=0

 

 

Let co-ordinate of A = (0,a)

Equation of parallel lines are 

x - y + 2 =0  and  7x -y + 3 = 0

Diagonals are \parallel to \angle bisectors  i.e.

\frac{x-y+2}{\sqrt{2}}=\pm \left ( \frac{7x-y+3}{5\sqrt{2}} \right )

i.e. L_{1} : \: 2x+4y-7=0

L_{2} : \: 12x-6y+13=0

m_{1}=\frac{-1}{2}  and  m_{2}=2

Slope of A(0,C)  to P(1,2)  is \frac{2-C}{1}=\frac{-1}{2}\: \Rightarrow \: C=\frac{5}{2}


Option 1)

\frac{5}{2}

Option 2)

\frac{7}{4}

Option 3)

2

Option 4)

\frac{7}{2}

Posted by

Himanshu

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