Where Does πr² Come From?
Slice, rearrange, discover
The animation plays automatically: a circle is sliced into 4 → 8 → 16 → 32 wedges and staggered into a row. See it? That row is a near-perfect parallelogram with base πr and height r.
Formula Animation
Watch the circle become a parallelogram — that’s the picture behind A = πr².
Slice & Rearrange
More slices → the pieces line up into a near-perfect parallelogram (base ≈ πr, height = r).
Cut the circle into 4 equal wedges and lay them in a row, alternating up and down.
4 slices