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Q37E
Expert-verifiedTo d\({\bf{b}} = \left\langle {{b_1},{b_2},{b_3}} \right\rangle \)escribe all set of points for condition \(\left| {{\bf{r}} - {{\bf{r}}_0}} \right| = 1\).
All set of points for condition \(\left| {{\bf{r}} - {{\bf{r}}_0}} \right| = 1\) is described and it forms a sphere with radius \(1\).
Subtraction of vectors:
Consider the two three-dimensional vectors such as \(a = \left\langle {{a_1},{a_2},{a_3}} \right\rangle \) and .
The vector subtraction of two vectors \((a - b)\) is,
\(\begin{aligned}{l}(a - b) &= \left\langle {{a_1},{a_2},{a_3}} \right\rangle - \left\langle {{b_1},{b_2},{b_3}} \right\rangle \\ &= \left\langle {{a_1} - {b_1},{a_2} - {b_2},{a_3} - {b_3}} \right\rangle \end{aligned}\)
Given:
Two three-dimensional vectors \({\bf{r}} = \langle x,y,z\rangle \) and \({{\bf{r}}_0} = \left\langle {{x_0},{y_0},{z_0}} \right\rangle \).
Consider the expression for magnitude of vector \(a = \left\langle {{a_1},{a_2},{a_3}} \right\rangle (|{\rm{a}}|)\).
\(|{\rm{a}}| = \sqrt {a_1^2 + a_2^2 + a_3^2} .......(1)\)
Write the expression for sphere with center \(C(h,k,l)\) and radius \(r\).
\({(x - h)^2} + {(y - k)^2} + {(z - l)^2} = {r^2}.......(2)\)
Write the expression for relation between vectors \(r\) and \({{\bf{r}}_0}\).
\(\left| {{\bf{r}} - {{\bf{r}}_0}} \right| = 1\)
From definition, substitute \(\langle x,y,z\rangle \) for \(r\) and \(\left\langle {{x_0},{y_0},{z_0}} \right\rangle \) for \({{\bf{r}}_0}\),\(\begin{aligned}{l}\left| {\langle x,y,z\rangle - \left\langle {{x_0},{y_0},{z_0}} \right\rangle } \right| = 1\\\left| {\left\langle {x - {x_0},y - {y_0},z - {z_0}} \right\rangle } \right| = 1.......(3)\end{aligned}\)
Find the value of \(\left| {\left\langle {x - {x_0},y - {y_0},z - {z_0}} \right\rangle } \right|\) by using equation (1).
\(\left| {\left\langle {x - {x_0},y - {y_0},z - {z_0}} \right\rangle } \right| = \sqrt {{{\left( {x - {x_0}} \right)}^2} + {{\left( {y - {y_0}} \right)}^2} + {{\left( {z - {z_0}} \right)}^2}} \)
Substitute \(\sqrt {{{\left( {x - {x_0}} \right)}^2} + {{\left( {y - {y_0}} \right)}^2} + {{\left( {z - {z_0}} \right)}^2}} \) for \(\left| {\left\langle {x - {x_0},y - {y_0},z - {z_0}} \right\rangle } \right|\) in equation (3), \(\sqrt {{{\left( {x - {x_0}} \right)}^2} + {{\left( {y - {y_0}} \right)}^2} + {{\left( {z - {z_0}} \right)}^2}} = 1\)
Take square on both sides of equation.
\(\begin{aligned}{l}{\left( {\sqrt {{{\left( {x - {x_0}} \right)}^2} + {{\left( {y - {y_0}} \right)}^2} + {{\left( {z - {z_0}} \right)}^2}} } \right)^2} &= {1^2}\\{\left( {x - {x_0}} \right)^2} + {\left( {y - {y_0}} \right)^2} + {\left( {z - {z_0}} \right)^2} &= {1^2}.......(4)\end{aligned}\)
Compare the equations (2) and (4), the equation (4) represents a sphere with radius \(1\).
Thus, all set of points for condition \(\left| {{\bf{r}} - {{\bf{r}}_0}} \right| = 1\) is described and it forms a sphere with radius \(1\).
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