Circles – chords and tangents

MathematicsPlane GeometryAges 14–15

Circle (O; R) with a chord AB and an external point M. Drag the chord's midpoint H to change the distance OH and see that OH ⟂ AB and AB = 2√(R² − OH²); drag M to see the two tangents MT₁ and MT₂ are equal with OT ⟂ MT; drag the point on the circle to change the radius. Once M moves inside the circle, no tangent exists.