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If \(\overrightarrow {PQ} = \left( {\begin{array}{*{20}{c}} a\\ b\\ c \end{array}} \right)\) then the magnitude of \(\overrightarrow {PQ}\) is written as \(\left| {\overrightarrow {PQ} } \right|\) and is calculated by the formula below:

\(\left| {\overrightarrow {PQ} } \right| = \sqrt {{a^2} + {b^2} + {c^2}}\)