Question 339911
Divide by the magnitude of {{{a}}}.
{{{abs(a)=sqrt((-10)^2+3^2+(-9)^2)}}}
{{{abs(a)=sqrt(100+9+81)}}}
{{{abs(a)=sqrt(190)}}}
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{{{u}}}=({{{-10/sqrt(190)}}},{{{3/sqrt(190)}}},{{{-9/sqrt(190)}}})