Vectors

• Dot product:

  a.b = ?

  |a||b| * cos@
• Angle between two vectors is the angle between their directions.
• How do you calculate if lines are perpendicular?

  Check if Dot product = 0
• If dot product = 0, then they're perpendicular.
• To find if lines are parallel:

  kD1=D2
• The line (L) at the shortest distance between 2 lines (L1, L2) has a direction vector that is perpendicular to L1 and L2