# 4-4 Notes for Algebra 1 - Southside High School 4-4 Notes for Algebra 1 Parallel and Perpendicular lines Parallel Lines Lines in the same plane that do not intersect. Non-vertical Parallel lines have the same slope. Example 1 pg. 239 Parallel Lines through a given point. Write an equation in slope-intercept form for the line that passes through and is parallel to the graph of . Example 1 pg. 239 Parallel Lines through a

given point. Write an equation in slope-intercept form for the line that passes through and is parallel to the graph of 7. Perpendicular lines Lines that intersect at right angles. The slopes of non-vertical perpendicular lines are opposite reciprocals. That means their product is . Example 2 pg. 240 slopes of perpendicular lines T

2 GEOMETRY The height of a trapezoid is the length of a segment that is E perpendicular to both bases. In trapezoidR ARTP, and are bases. 1 -5 -4 -2

-1 0 -1 -2 -3 -4 1.) Can be used to measure the height of the trapezoid? Explain. -5 -6

-7 Z 2.) Are the bases parallel -8 -9 A -10 1

2 P 3 4 5 6 7

Example 2 pg. 240 slopes of perpendicular lines T 2 GEOMETRY The height of a trapezoid is the length of a segment that is E perpendicular to both bases. In trapezoid ARTP,R and are bases. 1.) Can be used to measure the height of the trapezoid? Explain.

No, the slope of is 1, and the slope of is . since they are not perpendicular, it cannot be used as the height 2.) Are the bases parallel Yes, both have a slope of 1. 1 -5 -4 -2

-1 0 -1 -2 -3 -4 -5 1 2

3 4 P 5 6 7 Example 3 pg. 241 Parallel or Perpendicular lines

Determine whether the graphs of , and are parallel or perpendicular. Explain. Example 3 pg. 241 Parallel or Perpendicular lines Determine whether the graphs of , and are parallel or perpendicular. Explain. is parallel to , because they have equal slopes. is perpendicular to them both because the product of their slopes, and is Example 4 pg. 241 Perpendicular

lines through a given point. Write an equation in slope-intercept form for the line that passes through and is perpendicular to the graph of Example 4 pg. 241 Perpendicular lines through a given point. Write an equation in slope-intercept form for the line that passes through and is perpendicular to the graph of 4-4 pg. 243 11-37o, 39-41, 5172(x3)