The perpendiculars are drawn to lines $L_1$ and $L_2$ from the origin making an angle $\frac{\pi}{4}$ and $\frac{3\pi}{4}$ respectively with the positive direction of X-axis. If both the lines are at unit distance from the origin, then their joint equation is
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Geometry Tip: When multiplying lines to find joint equations, always look for groupings that create a difference of squares. It reduces the chance of algebraic errors compared to distributing every single term manually.