Find the angle between the lines whose direction cosines are given by the equations ltmath

cosines are given by the equations ltmath gt
ltmrow gt
ltmn gt3 lt/mn gt ltmi gtl lt/mi gt ltmo gt+ lt/mo gt ltmi gtm lt/mi gt ltmo gt+ lt/mo gt ltmn gt5 lt/mn gt ltmi gtn lt/mi gt ltmo gt= lt/mo gt ltmn gt0 lt/mn gt ltmo gt, lt/mo gt ltmo gt  lt/mo gt ltmn gt6 lt/mn gt ltmi gtm lt/mi gt ltmi gtm lt/mi gt ltmo gt− lt/mo gt ltmn gt2 lt/mn gt ltmi gtn lt/mi gt ltmi gtl lt/mi gt ltmo gt+ lt/mo gt ltmn gt5 lt/mn gt ltmi gtl lt/mi gt ltmo gt= lt/mo gt ltmn gt0 lt/mn gt lt/mrow gt
lt/math gt