Hi everyone! So I was looking at vectors and there is this topic which teaches you about using the dot product to find perpendicular lines. In the sense where AB // CD, AB.CD=0 right? However, the examples given in the book only uses the directional vector. E.g. You are given this line l1. Then you need to find the foot of the perpendicular from a point P to l1. So the example use the fact that F (foot of perpendicular) lies on l1 (which l1 vector parametric equation is given) to get the equation of OF and subsequently PF. However, they dot multiplied the PF with the direction vector of l1 and not the equation of l1 which is what I initially thought of. I know im misunderstanding something but not sure what it is. Thank you so much for any clarifications given.