Find the measure of the acute angle (in degrees) of intersection of lines \(L_1\) and \(L_2\) given by parametric equations
\[L_1:\quad x=t,\,y=t,\,z=0\]
\[L_2:\quad x=2t,\,y=t,\,z=t\]
\[\answer {30}\, \mbox {degrees}\]