Justify that the magnitude of the angle of intersection of $g _ { k }$ and the $x _ { 1 } x _ { 2 }$-plane is less than $30 ^ { \circ }$ if $2 k ^ { 2 } > 1$ holds.
Justify that the magnitude of the angle of intersection of $g _ { k }$ and the $x _ { 1 } x _ { 2 }$-plane is less than $30 ^ { \circ }$ if $2 k ^ { 2 } > 1$ holds.