SOLUTION: the line y=2x+7 is parallel to the line y=2x-3.The line y= -0.5x+7 is perpendicular to the line y=2x-3. Find the perpendicular distance between the pair of parallel lines.

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: the line y=2x+7 is parallel to the line y=2x-3.The line y= -0.5x+7 is perpendicular to the line y=2x-3. Find the perpendicular distance between the pair of parallel lines.      Log On


   



Question 978141: the line y=2x+7 is parallel to the line y=2x-3.The line y= -0.5x+7 is perpendicular to the line y=2x-3. Find the perpendicular distance between the pair of parallel lines.
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
Line blue%28y=2x-3%29 is parallel to line red%28y=2x%2B7%29 ,
which is perpendicular to green%28y=-0.5x%2B7%29 ,
so blue%28y=2x-3%29 and green%28y=-0.5x%2B7%29 are perpendicular to each other.
So the distance between blue%28y=2x-3%29 and red%28y=2x%2B7%29
is the distance, along green%28y=-0.5x%2B7%29 ,
between the points where green%28y=-0.5x%2B7%29 intersects the other two lines.
Lines green%28y=-0.5x%2B7%29 and red%28y=2x%2B7%29 obviously intersect at point Q%280%2C7%29 , the y-intercept for both lines.
We can find the point P where green%28y=-0.5x%2B7%29 and blue%28y=2x-3%29 intersect
by solving system%28green%28y=-0.5x%2B7%29%2Cblue%28y=2x-3%29%29
I wanted to graph anyway, and in the graph it looked like it was P%284%2C5%29 .
Substituting x=4 to see that y=5 for both lines confirmed that solution:
green%28y=-0.5%2A4%2B7=-2%2B7=5%29 and blue%28y=2%2A4-3=8-3=5%29%29


The distance from Q%7B0%2C7%29 and P%284%2C5%29
is the distance between red%28y=2x%2B7%29 and blue%28y=2x-3%29 .
The distance between two points can be calculated according to a formula:
PQ=sqrt%28%28x%5BP%5D-x%5BQ%5D%29%5E2%2B%28y%5BP%5D-y%5BQ%5D%29%5E2%29 ,
but there is no need (usually) to memorize formulas,
if you understand their meaning.
That distance is the hypotenuse of a right triangle,
like the one in my drawing,
whose legs, parallel to the x-axis and y-axis,
are the horizontal distance and the vertical distance between the points.
In this case,
distance=sqrt%284%5E2%2B2%5E2%29=sqrt%2816%2B4%29=sqrt%2820%29=2sqrt%285%29=about4.47(rounded).