Distance between point and line

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SUMMARY

The discussion focuses on deriving the equation of a line passing through the origin (0,0) given specific distance constraints from points A(2,1) and B(1,4). The formula used for calculating the distance from a point to a line is \(d=\frac{\left | Ax+By+C \right |}{\sqrt{A^{2}+B^{2}}}\). The user simplifies the problem by recognizing that since the line passes through the origin, the constant \(C\) equals 0, leading to the family of lines represented as \(Ax+y=0\). The key challenge is solving the equation with one variable after substituting the known distance condition.

PREREQUISITES
  • Understanding of linear equations and their graphical representation.
  • Familiarity with the distance formula from a point to a line.
  • Basic algebraic manipulation skills.
  • Knowledge of coordinate geometry concepts.
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  • Explore the derivation of the distance formula from a point to a line in more depth.
  • Study the properties of lines in coordinate geometry, particularly lines through the origin.
  • Learn about systems of equations and methods for solving them with multiple variables.
  • Investigate the geometric interpretation of distance constraints in linear equations.
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Students and professionals in mathematics, particularly those studying geometry and algebra, as well as educators looking for practical examples of distance calculations in coordinate systems.

Yankel
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Hello all,

I need your assistance with the following:

Find the equation of the line that goes through the origin (0,0) if it is known that the sum of distances of the line from A(2,1) and B(1,4) is equal to \[\sqrt{8}\], and it is also known that the line is between the points.

The formula I am supposed to use is:

\[d=\frac{\left | Ax+By+C \right |}{\sqrt{A^{2}+B^{2}}}\]

What I did, is I set the equation to be:

\[\frac{-2A-B-C}{\sqrt{A^{2}+B^{2}}}+\frac{A+4B+C}{\sqrt{A^{2}+B^{2}}}=\sqrt{8}\]

The absolute value was omitted since the line is between the points, i.e. one point is below and one above.

I am stuck with 1 equation and 2 variables. How do I proceed ? Since the point (0,0) is on the line, I know that C is 0 in the equation Ax+By+C=0, but this parameter is not important anyway (C-C=0).

Thank you !
 
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The family of lines passing through the origin may be written:

$$Ax+y=0$$

where the slope is $-A$. Now you will have only 1 variable in your equation. ;)
 

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