2'3 Parallel and Perpendicular Lines in a Coordinate Plane

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2.3 Parallel and Perpendicular Lines in a
Coordinate Plane
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Slope

• Vertical Change over Horizontal Change
• Rise over run
• M y2 y1
• x2 x1
• Positive Slop Negative Slope Zero Slope Slope
  Undefined

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Slopes of Parallel and Perpendicular Lines

• Slopes of non-vertical lines are
• Two lines with same slope are //
• Vertical lines are //
• The product of the slopes of 2 perpendicular
  lines, neither line can be vertical, is -1
• If the product of to the slope of two lines is -1
  then the lines are //
• A horizontal and vertical line are perpendicular

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Theorem 2.5 2.6

• Two lines // to a 3rd line are // to each other
• In a plane, two lines perpendicular to a 3rd line
  are // to each other

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Slope Intercept

• Y (m)b b
• Where
• m slope
• b y intercept
• Graph y ¾ x 2

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Homework

• Page 86 1-19