Posted by **Peter** on Thursday, October 28, 2010 at 2:41am.

Determine the diameter of the largest circle that can be drawn between the parallel lines y=2x and y=2x-5.

- MATH -
**bobpursley**, Thursday, October 28, 2010 at 2:54am
What is the distance between them?

find the perpendicular line

y=-1/2 x + b

pick a point on the first line: say, 1,2

2= -1/2 *1+b

b=2.5

y= -.5x+2.5 is the perpendicular line.

now, what point does this line intersect the second parallel line?

y=-.5x+2.5

y=2x-5

or 2x-5=-.5x+2.5

2.5x=7.5

x=3

y=2x-5=1

distance between points 1,2 and 3,1

d= sqrt (2^2 + 1^2)=sqrt5

check all that math, I did it in my head.

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