Question:medium

The equations of the lines passing through the point \( (1,0) \) and at a distance \( \frac{\sqrt{3}}{2} \) from the origin are

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Use slope form for line through a point, then apply distance formula to find possible slopes.
Updated On: Jun 17, 2026
  • \( \sqrt{3}x + y - \sqrt{3} = 0, \; \sqrt{3}x - y - \sqrt{3} = 0 \)
  • \( \sqrt{3}x + y + \sqrt{3} = 0, \; \sqrt{3}x - y + \sqrt{3} = 0 \)
  • \( x + \sqrt{3}y - \sqrt{3} = 0, \; x - \sqrt{3}y - \sqrt{3} = 0 \)
  • None of the above
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The Correct Option is A

Solution and Explanation

To find the equations of the lines passing through the point \( (1,0) \) and at a distance \( \frac{\sqrt{3}}{2} \) from the origin, follow these steps:

  1. \(d = \frac{|Ax_1 + By_1 + C|}{\sqrt{A^2 + B^2}}\)

where \( A, B, C \) are the coefficients of a line equation in the form \( Ax + By + C = 0 \), and \( (x_1, y_1) \) is a point on the line. Here, the distance \( d \) from the origin to the line is given as \( \frac{\sqrt{3}}{2} \).

Substitute the point \( (1, 0) \) into the line equation \( Ax + By + C = 0 \) to find the possible forms of \( C \):

\(A \cdot 1 + B \cdot 0 + C = A + C = 0 \Rightarrow C = -A\)

Plug in the distance formula for \( d = \frac{\sqrt{3}}{2} \):

  1. \(\frac{|C|}{\sqrt{A^2 + B^2}} = \frac{\sqrt{3}}{2}\)

Using the condition \( C = -A \), substitute in the above equation:

\(\frac{|A|}{\sqrt{A^2 + B^2}} = \frac{\sqrt{3}}{2}\)

Squaring both sides, we get:

\(\frac{A^2}{A^2 + B^2} = \frac{3}{4}\)

Solving for the relationship between \( A \) and \( B \), we get:

\(4A^2 = 3A^2 + 3B^2 \Rightarrow A^2 = 3B^2 \Rightarrow \frac{A}{B} = \pm\sqrt{3}\)

Thus, the line equations become:

  • For \(\frac{A}{B} = \sqrt{3}\), the equation is: \(\sqrt{3}x + y + C = 0 \Rightarrow \sqrt{3}(1) + 0 + C = 0\)

\( C = -\sqrt{3} \), so the equation is \( \sqrt{3}x + y - \sqrt{3} = 0 \).

  • For \(\frac{A}{B} = -\sqrt{3}\), the equation is: \(\sqrt{3}x - y + C = 0 \Rightarrow \sqrt{3}(1) - 0 + C = 0\)

\( C = -\sqrt{3} \), so the equation is \( \sqrt{3}x - y - \sqrt{3} = 0 \).

Therefore, the correct equations are \( \sqrt{3}x + y - \sqrt{3} = 0 \) and \( \sqrt{3}x - y - \sqrt{3} = 0 \).

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