Geometry

Tangent-Chord Angle

Acute angle formed by a chord of a circle and a tangent to the circle at one of the endpoints of the chord.

Example

In the figure below, angle BAC is a tangent-chord angle to the circle with centre O. The point of tangency is the endpoint A of chord AB. Line segment AC is a tangent to the circle at point A.

Formula

In the example above, m[latex]\angle {\textrm{BAC}}=\frac{\textrm{m}\angle{\textrm{AOB}}}{2}[/latex]

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