1. The problem statement, all variables and given/known data I'm given a vector (x,y,[tex]\alpha[/tex]) (cant state exact number cause of plagarism). I have to find the value of [tex]\alpha[/tex] which make the vector perpendicular to a plane. I also have 2 other vectors that are parallel to the plane. 2. Relevant equations dot product. 3. The attempt at a solution I found the value of [tex]\alpha[/tex] that is perpendicular to the 2 line parallel to the plane, but it is different from the value i get if i calculate the vector to be perpendicular to the plane itself. Infact, the [tex]\alpha[/tex] value perpendicular to the plane is a multiple of the [tex]\alpha[/tex] value perpendicular to the 2 vectors parallel to the plane, and its also a different sign. I want to know what is the reason for this and am i doing something wrong? shouldnt i get the same value since the 2 vectors and the plane are parallel?