Drag the circles. Classification by d vs r1+r2 / |r1-r2|, the a/h construction, and the lens area.
Tip: drag a circle's center dot to move it. Use the sliders to resize.
| Operation | Time | Note |
|---|---|---|
| Center distance d | O(1) | 1 hypot |
| Classify | O(1) | 2 comparisons |
| Intersect (a/h) | O(1) | 1 sqrt |
| Lens area | O(1) | 2 acos |
| Overlap test (no sqrt) | O(1) | d² ≤ (r1+r2)² |