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## Homework Statement

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.

## Homework Equations

dot product.

## 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?