Question:hard

Suppose \(P(x,y)\) lying on \[ \sqrt{3}x-y+2=0 \] or \[ \sqrt{3}x+y-2=0 \] is at a distance of \(5\) units from their point of intersection. Then the distance from \((0,0)\) to the foot of the perpendicular of \(P\) onto the \(y\)-axis is

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If a point moves a distance \(r\) along a line making angle \(\theta\) with the positive \(x\)-axis, then its vertical change is \[ r\sin\theta. \]
Updated On: Jun 24, 2026
  • \(2+\frac{5\sqrt{3}}{2}\)
  • \(\frac{5\sqrt{3}}{2}\)
  • \(2\)
  • \(2-\frac{5\sqrt{3}}{2}\)
Show Solution

The Correct Option is A

Solution and Explanation

Step 1: Find the intersection of the two lines.
The lines are $\sqrt{3}x - y + 2 = 0$ and $\sqrt{3}x + y - 2 = 0$. Adding: $2\sqrt{3}x = 0$, so $x = 0$, then $y = 2$. Intersection is $(0, 2)$.

Step 2: Find the angle each line makes with the x-axis.
Line 1: $y = \sqrt{3}x + 2$ has slope $\sqrt{3}$, so it makes angle $60°$ with x-axis. Line 2: $y = 2 - \sqrt{3}x$ has slope $-\sqrt{3}$, angle $120°$. The angle between them is $60°$, so they are symmetric about the y-axis.

Step 3: Place P on Line 1 at distance 5 from $(0,2)$.
Direction vector of Line 1 is $(\cos 60°, \sin 60°) = (1/2, \sqrt{3}/2)$. So $P = (0 + 5 \cdot \frac{1}{2},\ 2 + 5 \cdot \frac{\sqrt{3}}{2}) = \left(\frac{5}{2},\ 2 + \frac{5\sqrt{3}}{2}\right)$, or the other side $P = \left(-\frac{5}{2},\ 2 - \frac{5\sqrt{3}}{2}\right)$.

Step 4: Find the foot of perpendicular of P onto the y-axis.
The foot of perpendicular from $(x_0, y_0)$ onto the y-axis is $(0, y_0)$. So its distance from origin is $|y_0|$.

Step 5: Compute the distances.
For $P = \left(\frac{5}{2},\ 2 + \frac{5\sqrt{3}}{2}\right)$: distance from origin to foot $= 2 + \frac{5\sqrt{3}}{2}$ (positive, so this is the answer).

Step 6: Verify the other case.
For $P = \left(-\frac{5}{2},\ 2 - \frac{5\sqrt{3}}{2}\right)$: foot is $(0, 2 - \frac{5\sqrt{3}}{2})$, distance $= \left|2 - \frac{5\sqrt{3}}{2}\right|$. Since $\frac{5\sqrt{3}}{2} \approx 4.33 > 2$, this is negative inside. So this equals $\frac{5\sqrt{3}}{2} - 2$. The question asks for distance from origin, so both are valid but the matching option is $2 + \frac{5\sqrt{3}}{2}$.
\[ \boxed{2 + \dfrac{5\sqrt{3}}{2}} \]
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