Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Line Parallel to the Plane Equation (Final Exam Review)

  1. Jun 10, 2008 #1
    1. The problem statement, all variables and given/known data
    Explain why the line <x,y,z> = <3,1,4> + t<4,-5,2> is parallel to the plane with equation 2x + 2y +z = 7

    2. Relevant equations
    The normal vector of <x,y,z> [4,-5,2] and the plane equation 2x + 2y + z = 7

    3. The attempt at a solution
    Well, I'm trying to review for the final exam and I'm missing a crucial notes sheet.

    So, I attempted to do the dot product of the normal vector and the plane equation vector which is:

    4*2 + -5*2 + 1*2 = 0

    However, that didn't add up to 7 which would mean == lines.

    Though, I think by writing out the dot product I technically proved perpendicularity since plane equations are based off a vector and a point. Thus, making it perpendicular to that point.

    So if two bits are perpendicular to the same point then they are parallel to each other.

    Any help, would be much appreciated.
  2. jcsd
  3. Jun 10, 2008 #2
    Yes, that's correct. If the line <x,y,z> = <3,1,4> + t<4,-5,2> is parallel to the plane, then its direction vector i.e. (4,-5,2) is perpendicular to the plane's normal vector.
  4. Jun 10, 2008 #3
    Thank You So Much!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook