Mathematics · 10

Circle Theorems

Circle theorems are fundamental geometric principles about circles, angles, chords, tangents, and arcs. These theorems help solve problems related to

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Why is the angle in a semicircle always 90°?

A semicircle has a central angle of 180°. By inscribed angle theorem, any inscribed angle is half the central angle. Therefore, inscribed angle = 180°/2 = 90°.

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What is the alternate segment theorem and when is it used?

The alternate segment theorem states: The angle between a tangent and a chord equals the inscribed angle in the alternate segment. It is used when you have a tangent and chord meeting at a point on the circle.

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How are tangent-chord angles different from inscribed angles?

Both equal half the arc they subtend, but are measured differently. Inscribed angle is measured from two points on circle. Tangent-chord angle is measured between a tangent line and a chord at their point of intersection on the circle.

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