Home > Distance formula, Equation of perpendicular bisector

Distance formula, Equation of perpendicular bisector - (Concept)

Distance between two points $\mathrm{A}\left(\mathrm{z}_1\right)$ and $\mathrm{B}\left(\mathrm{z}_2\right)$ is

$
A B=\left|z_2-z_1\right|=\mid \text { Affix of } B-\text { Affix of } A \mid
$

Let $\mathrm{z}_1=\mathrm{x}+\mathrm{iy}$ and $\mathrm{z}_2=\mathrm{x}+\mathrm{iy}$ Then,$\left|z_1-z_2\right|=\left|\left(x_1-x_2\right)+i\left(y_1-y_2\right)\right|$$=\sqrt{\left(\mathrm{x}_1-\mathrm{x}_2\right)^2+\left(\mathrm{y}_1-\mathrm{y}_2\right)^2}$$=$ distance between points $\left(\mathrm{x}_1, \mathrm{y}_1\right)$ and $\left(\mathrm{x}_2, \mathrm{y}_2\right)=$ distance between between $\mathrm{z}_1$ and $\mathrm{z}_2$ where $\mathrm{z}_1=\mathrm{x}_1+\mathrm{iy}_1$ and $\mathrm{z}_2=\mathrm{x}_2+\mathrm{iy}_2$

The distance of a point from the origin is $|z-0|=|z|$
Three points $A\left(z_1\right), B\left(z_2\right)$ and $C\left(z_3\right)$ are collinear, then $A B+B C=A C$

i.e. $\left|z_2-z_1\right|+\left|z_3-z_2\right|=\left|z_3-z_1\right|$

Perpendicular bisector

We can use the distance formula to find the equation of perpendicular bisector

Let two fixed points A(z1) and B(z2) and a moving point C(z) which lies on the perpendicular bisector of AB

As any point on the perpendicular bisector of AB will be equidistant from A and B, so

$
\begin{aligned}
& A C=B C \\
& \left|z-z_1\right|=\left|z-z_2\right|
\end{aligned}
$
This is the equation of perpendicular to the bisector of $A B$, where $A\left(z_1\right)$ and $B\left(z_2\right)$.

Exam Chapter
JEE MAIN Complex numbers and quadratic equations
Algebra (Arihant)
Page No. : 35
Line : 6

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