The joint equation of the pair of lines through the origin and making an equilateral triangle with the line…

The joint equation of the pair of lines through the origin and making an equilateral triangle with the line $x=3$ is
  1. $3 x^2-y^2=0$
  2. $\sqrt{3} x^2-2 x y+y^2=0$
  3. $x^2-3 y^2=0$
  4. $x^2+2 x y-\sqrt{3} x^2=0$

Solution

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 $(x-\sqrt{3 y})(x+\sqrt{3 y})=0 \text { i.e. } x^2-3 y^2=0$

Asked in: MHT CET 2021 (20 Sep Shift 1)

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