The angle between  i^ line of the intersection of the plane r→⋅(i^+2j^+3k^)=0 and r→⋅(3i^+3j^+k^)=0 is

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  cos⁡θ=749+64+9=7122