WOLFRAM|DEMONSTRATIONS PROJECT

Tangent Circles to Two Parallel Lines and Passing through a Point

slope

m

1.2

y intercepts

b

1

2.1

b

2

5

coordinates of red point

x

7.8

y

13.7

This Demonstration is based on an example from a Wolfram Education Group seminar: Given two parallel lines and a point

P

between them, draw circles of radius

r

centered at

Q

1

and

Q

2

through

P

and tangent to the lines. Then the circle centered at

P

with radius

r

passes through

Q

1

and

Q

2

.

Here we allow the two blue circles to be constructed when the point is not between the two lines.