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Question: Answered & Verified by Expert
The joint equation of the pair of lines through the origin and making an equilateral triangle with the line $x=3$ is
MathematicsPair of LinesMHT CETMHT CET 2021 (20 Sep Shift 1)
Options:
  • A $3 x^2-y^2=0$
  • B $\sqrt{3} x^2-2 x y+y^2=0$
  • C $x^2-3 y^2=0$
  • D $x^2+2 x y-\sqrt{3} x^2=0$
Solution:
1268 Upvotes Verified Answer
The correct answer is: $x^2-3 y^2=0$


Slope of line $\mathrm{OA}=\tan 30^{\circ}=\frac{1}{\sqrt{3}}$ and
Slope of line $\mathrm{OB}=\tan \left(-30^{\circ}\right)=\frac{-1}{\sqrt{3}}$
$\therefore$ Equation of $\mathrm{OA}$ is $\mathrm{y}=\frac{1}{\sqrt{3}} \mathrm{x}$ and equation of $\mathrm{OB}$ is $\mathrm{y}=\frac{1}{\sqrt{3}} \mathrm{x}$ Hence required equation is
$$
(x-\sqrt{3 y})(x+\sqrt{3 y})=0 \text { i.e. } x^2-3 y^2=0
$$

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