Triangle Angle Lab
Drag any vertex. The three angles change — but their sum never does. Flip on the exterior angle to see it match the two remote interiors.
Draggable triangle
Drag any gold vertex. Angles are measured live.
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∠A
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∠B
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∠C
∠A + ∠B + ∠C = 180°
Controls
Show exterior angle at C
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