Let A, B, C be three points whose position vectors respectively are: 
$\begin{array}{l}\overrightarrow{\mathrm{a}}=\widehat{\mathrm{i}}+4\widehat{\mathrm{j}}+3\widehat{\mathrm{k}}\\ \overrightarrow{\mathrm{b}}=2\widehat{\mathrm{i}}+\mathrm{\alpha }\widehat{\mathrm{j}}+4\widehat{\mathrm{k}},\mathrm{\alpha }\in \mathrm{ℝ}\\ \overrightarrow{\mathrm{c}}=3\widehat{\mathrm{i}}-2\widehat{\mathrm{j}}+5\widehat{\mathrm{k}}\end{array}$
If αis the smallest positive integer for which$\overrightarrow{\mathrm{a}},\overrightarrow{\mathrm{b}},\overrightarrow{\mathrm{c}}$are non-collinear, then the length of the median, in $\mathrm{△}\mathrm{ABC},$through A is: