Mathematics

Problem

Given

\vec{a}=3\mathbf{i}-\mathbf{j}+4\mathbf{k}

and

\vec{b}=5\mathbf{i}+12\mathbf{j}

, the value of

\cos\theta

, where

\theta

is the angle between

\vec{a}

and

\vec{b}

, is a)

\dfrac{15}{13\sqrt{26}}

\dfrac{3}{\sqrt{26}}

\dfrac{3}{13\sqrt{26}}

\dfrac{3}{13\sqrt{10}}