Geometry: Parallel and Perpendicular Lines

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Lesson 5-6

• Geometry Parallel and Perpendicular Lines

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Transparency 6
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display the answers.
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Transparency 6a
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Objectives

• Locate points on the coordinate plane
• Graph points on a coordinate plane
• Write an equation of the line that passes through
  a given point, parallel to a given line
• Write an equation of the line that passes through
  a given point, perpendicular to a given line

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Vocabulary

• Coordinate plane an x-y grid with axes as
  reference lines
• Quadrant the axes divide the coordinate plane
  into 4 regions or quadrants
• Graph is a plot of an ordered pair (x,y) on the
  coordinate plane
• Parallel lines lines in the same plane that
  never intersect and have the same slope
• Perpendicular lines lines that meet to form
  right angles

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x-y Coordinate Plane
Quadrants
Point Plotting
I
II
up 7
left 4
right 5
III
IV
down 8
(x, y) (-4, 7) (5, -8) x left or
right y up or down
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Example 1
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Example 1 cont
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Example 2
Step 1 Find the slope of the given line.
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Example 2 cont
Step 3 Use the point-slope form to find the
equation.
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Example 2 cont
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Example 3
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Example 3 cont
Step 2 The slope of the given line is -5/2. So,
the slope of the line perpendicular to this line
is the opposite reciprocal of -5/2 or 2/5.
Step 3 Substitute the slope and the given point
into the point-slope form of a linear equation.
Then write the equation in slope-intercept form.
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Summary Homework

• Summary
• Two nonvertical lines are parallel if they have
  the same slope
• Two nonvertical lines are perpendicular if the
  product of their slopes is -1
• Homework
• Pg 296 14-40 even