then/now you proved that two lines are parallel using angle relationships. find the distance between...
Post on 18-Jan-2016
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You proved that two lines are parallel using angle relationships.
• Find the distance between a point and a line.
• Find the distance between parallel lines.
• equidistant
Distance Between Parallel Lines
Find the distance between the parallel lines a and b whose equations are y = 2x + 3 and y = 2x – 1, respectively.
You will need to solve a system of equations to find the endpoints of a segment that is perpendicular to both a and b. From their equations,we know that the slope of line a and line b is 2.
Sketch line p through they-intercept of line b, (0, –1),perpendicular to lines a and b.
a b
p
Distance Between Parallel Lines
Step 1
Use the y-intercept of line b, (0, –1), as one of the endpoints of the perpendicular segment.
Write an equation for line p. The slope of p is the
opposite reciprocal of
Point-slope form
Simplify.
Subtract 1 from each side.
Distance Between Parallel Lines
Use a system of equations to determine the point of intersection of the lines a and p.
Step 2
Substitute 2x + 3 for y in the second equation.
Group like terms on each side.
Distance Between Parallel Lines
Simplify on each side.
Multiply each side by .
Substitute for x in the
equation for p.
Distance Between Parallel Lines
Simplify.
The point of intersection is or (–1.6, –0.2).
Distance Between Parallel Lines
Use the Distance Formula to determine the distance between (0, –1) and (–1.6, –0.2).
Step 3
Distance Formula
x2 = –1.6, x1 = 0, y2 = –0.2, y1 = –1
Answer: The distance between the lines is about 1.79 units.
A. 2.13 units
B. 3.16 units
C. 2.85 units
D. 3 units
Find the distance between the parallel lines a and b
whose equations are and ,
respectively.
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