# Math 22 The Three-Dimensional Coordinate System

## The Distance and Midpoint Formulas

 The distance ${\displaystyle d}$ between the points ${\displaystyle (x_{1},x_{2},x_{3})}$ and ${\displaystyle (x_{2},y_{2},z_{2})}$ is

${\displaystyle d={\sqrt {(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}+(z_{2}-z_{1})^{2}}}}$


Exercises 1 Find the distance between two points

1) ${\displaystyle (4,2,3)and[itex](1,2,0)}$

Solution:
${\displaystyle d={\sqrt {(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}+(z_{2}-z_{1})^{2}}}={\sqrt {(1-4)^{2}+(2-2)^{2}+(0-3)^{2}}}={\sqrt {18}}}$

2) ${\displaystyle (1,2,4)and[itex](2,5,1)}$

Solution:
${\displaystyle d={\sqrt {(2-1)^{2}+(5-2)^{2}+(1-4)^{2}}}={\sqrt {19}}}$