(r ,. ,i)^2 + (r ,. ,j)^2 + (r ,. ,k)^2 = - Vidyadip

MCQ

${(r\,.\,i)^2} + {(r\,.\,j)^2} + {(r\,.\,k)^2} = $

A
$3{r^2}$
✓
${r^2}$
C
$0$
D
None of these

✓

Answer

Correct option: B.

${r^2}$

b
(b) Let $r = xi + yj + zk$ $ \Rightarrow r\,.\,i = x,$ $r\,.\,j = y,$ $r\,.\,k = z$

$ \Rightarrow {(r\,.\,i)^2} + {(r\,.\,j)^2} + {(r\,.\,k)^2} = {x^2} + {y^2} + {z^2} = {r^2}.$

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