Definition of Slope

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Definition of Slope

• The slope of a non-vertical line that contains
  the points(x1, y1) and (x2,y2) is equal to the
  ratio (x1, y1) / (x2,y2) .
• A(5,-3) B(2,3), slope 3-(-3)/2-5 6/-3 -2

2
Parallel Line Theorem

• Two non-vertical lines are parallel if and only
  if they have the same slope.
• Any two vertical lines are parallel.

3
Perpendicular Line Theorem

• Two non-vertical lines are perpendicular if and
  only if the product of their slopes is 1.
• Any vertical line is perpendicular to any
  horizontal line.

4
Midpoint Formula

• The midpoint of a segment with endpoints (x1, y1)
  and (x2, y2) has the following coordinates
• (x1 x2/2, y1y2/2)
• Ex A(0,0), B(4,2)
• (04/2, 02/2) (4/2, 2/2) (2,1)

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Parallel or Perpendicular?

• If two lines have the SAME slope they are
  parallel
• (-1,1) and (2,3) (2,2) and (5,4)
• 3-1/2-(-1) 2/3
• 4-2/5-2 2/3
• If the slope of the two lines is (-1) they are
  perpendicular
• Mlt AC -6-(-1)/2-(-1) -5/3
• Mlt BC 5-(-1)/ 9-(-1) 3/5
• -5/3 3/5 -1

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The End