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The equation of the lines through the point (2,3) and making an intercept of length 2 units between the lines \mathrm{y+2 x=3 \: and \: y+2 x=5}are
 

Option: 1

\mathrm{x-2=0,3 x+4 y=18}
 


Option: 2

\mathrm{x+3=0,3 x+4 y=12}
 


Option: 3

\mathrm{y-2=0,4 x-3 y=6}
 


Option: 4

none of these


Answers (1)

best_answer

Let line through \mathrm{A(2,3)} be

\mathrm{\frac{x-2}{\cos \theta}=\frac{y-3}{\sin \theta} =A B, B C }

            \mathrm{ =\lambda, \lambda+2}

\therefore \mathrm{B} is \mathrm{(2+\lambda \cos \theta, 3+\lambda \sin \theta)} which lies on \mathrm{y+2 x=3}..........(1)

The condition is \mathrm{3+\lambda \sin \theta+2(2+\lambda \cos \theta)=3}

Similarly, the condition for \mathrm{C(2+(\lambda+2) \cos \theta, 3+(\lambda+2) \sin \theta)}is

\mathrm{3+(\lambda+2) \sin \theta+2\{2+(\lambda+2) \cos \theta\}=5}..........(2)

On eliminate \lambda from (1) and (2), we obtain

\mathrm{2 \sin \theta+4 \cos \theta=2 }

\mathrm{\Rightarrow 2 \cos \theta=1-\sin \theta \text { or } 4\left(1-\sin ^2 \theta\right)=(1-\sin \theta)^2 }

\mathrm{\Rightarrow \sin \theta=1 \text { or } 4(1+\sin \theta)=1-\sin \theta }

\mathrm{\Rightarrow \theta=\frac{\pi}{2} \text { and } \sin \theta=-\frac{3}{5} \Rightarrow \tan \theta=\infty,-\frac{3}{4} }

The lines are \mathrm{x-2=0 \: and \: 3 x+4 y=18}.

Hence option 1 is correct.

Posted by

Gaurav

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