# Solve for r in (x-x1)^2 + (y-y1)^2 == (r+r1)^2 ?

Getting start with Sage. I tried a simply problem:

```
solve([(x-x1)^2 + (y-y1)^2 == (r+r1)^2, r)
```

Presumably the solution is +/- sqrt((x-x1)^2 + (y-y1)^2) - r1, but Sage never returns. Did I issue the right command?