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
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Circumference C
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Area A
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Arc length
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Sector area
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Fraction of circle
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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.