A circle and a tangent - Math Central

HOME

Math Central

Quandaries & Queries

Question from Lindsay, a student:

Hello. I'm trying to do a math problem and have searched the internet for equations but have come up empty handed. If you could help, that would be greatly appreciated!
The problem is stated thus: A circle is tangent to the y-axis at y=3 and has one x-intercept at x=1.
a. Determine the other x-intercept
b. deduce the equation of the circle.

Thanks!

Hi Lindsay,

The first thing I would do is draw a diagram and label some points.

circle

Since the distance from the centre of the circle C to P is r

(r - 1)² + (3 - 0)² = r²

Solve for r.

I hope this helps,
Penny

Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.