1. The problem statement, all variables and given/known data Find the equation of the line through the point (-5,-4,2) that intersects the line at r = (7,-13,8) +t(1,2,-2) at 90 degrees. 2. Relevant equations I guess that using the dot product for the direction vector of the line needed, (x,y,z) , with the direction of the given line will = 0. Then i get lost as to what I should be doing afterwards, in incorporating the point given with the variables that result from the dot product. 3. The attempt at a solution So i did (x,y,z) dot (1,2,-2) to get x +2y -2z = 0 at this point, i'm not sure where to do. Btw, the answer is r = (-5,-4,2) +t(14,-5,2).