Skill: circles
Lab: Circle Explorer
Drag the gold handle to change the radius, and slide the angle to carve out a sector.
Watch circumference, area, arc length, and sector area update live (π = 3.14).
Explorer
Drag the gold handle on the radius. The sector wedge follows the angle slider.
Radius r
—
Circumference C
—
Area A
—
Arc length
—
Sector area
—
Fraction of circle
—
Controls
Radius is in cm; everything rounds to 2 decimals.
Experiment 1 — doubling the radius. Set r = 4 cm and note C and A. Now double to r = 8 cm.
Circumference doubles (2πr is linear in r), but area quadruples (πr² squares r).
Experiment 2 — the half-circle check. Set θ = 180° with r = 6 cm.
The arc should read exactly half the circumference: 18.84 cm.
Experiment 3 — diameter thinking. r = 5 cm is the same circle as d = 10 cm.
Verify: C = 3.14 × 10 = 31.40 cm either way.
Verify: C = 3.14 × 10 = 31.40 cm either way.