The Vector −−→OA=−2^i+^j+2^k is rotated through an angle 90∘ about origin (O)In new Position it passes through ^i+^k. Then the vector in new position is
3(2^i+2^j+^k)
Vector perpendicular to →a and lie on the plane of →a&→b is parallel to (→a×→b)×→a=(→a.→a)→b−(→b.→a)=9(j+k)−3(−2i+j+2k)=3(2i+2j+k)