Angle between two unit-magnitude coplanar vectors P(0.866, 0.500, 0) and Q(0.259, 0.966, 0) will be

$\overrightarrow{P}=0.866\widehat{i}+0.500\widehat{j}+0\widehat{k},\left|\overrightarrow{P}\right|=1$
$\overrightarrow{Q}=0.259\widehat{i}+0.966\widehat{j}+0\widehat{k},\left|\overrightarrow{Q}\right|=1$
$\text{ Angle between two vectors }\overrightarrow{P}\text{ and }\overrightarrow{Q}\text{, }$
$\cos \theta =\frac{\overrightarrow{P}\cdot \overrightarrow{Q}}{\left|\overrightarrow{P}\right|\left|\overrightarrow{Q}\right|}$

$\begin{array}{l}\cos \theta =(0.866,0.500,0)\cdot (0.259,0.966,0)\\ \cos \theta =0.224+0.483\\ \cos \theta =0.707\\ \therefore \theta ={45}^{\circ }\end{array}$