# Finding intersection to two circles given one point
**URL:** https://boards.straightdope.com/t/finding-intersection-to-two-circles-given-one-point/505640
**Category:** Factual Questions
**Created:** [August 7, 2009, 3:02pm UTC](https://boards.straightdope.com/t/finding-intersection-to-two-circles-given-one-point/505640 "2009-08-07T15:02:52Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Edward\_The\_Head](https://boards.straightdope.com/u/Edward_The_Head)
#### Post date: [August 7, 2009, 3:02pm UTC](https://boards.straightdope.com/t/finding-intersection-to-two-circles-given-one-point/505640/1 "2009-08-07T15:02:52Z")
I hope I can explain this correctly, and I do have a picture of what I’m trying to do.
From the diagram this is what I’m trying to figure out. The odd symbol after the R, C2, and I is supposed to be a ?, but doesn’t come up in Microstation.
There is a known circle, with known Radius and center point, R and C1. There is also a known point in space, P, and a known line L. What I’d like to do is find the circle that goes through the unknown point I? and through P. The R? line from P is perpendicular to L.
What I’ve been doing is making a circle off of L running it down R? until it just touches around I?. This works, but is hard to make exact and sometimes hard to see. If I could find one of the three unknowns then making the circle would be easy. Is there an easier way to do this?
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### Author:  [@Gfactor](https://boards.straightdope.com/u/Gfactor)
#### Post date: [August 7, 2009, 3:18pm UTC](https://boards.straightdope.com/t/finding-intersection-to-two-circles-given-one-point/505640/2 "2009-08-07T15:18:54Z")
Closed as duplicate.
**Gfactor**
General Questions Moderator