The angle between i^ line of the intersection of the plane r→⋅(i^+2j^+3k^)=0 and r→⋅(3i^+3j^+k^)=0 is
cos−113
cos−123
none of these
Line of intersection of r→⋅(i^+2j^+3k^)=0 and r→⋅(3i^+3j^+k^)=0 will be Parallel to
(3i^+3j^+k^)×(i^+2j^+3k^), i.e., 7i^−8j^+3k^
If the required angle is θ then
cosθ=749+64+9=7122