lightbulb Key Concepts

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1. Basic Terms

• Chord: A line segment joining any two points on the circle.
• Diameter: The longest chord passing through the center.
• Tangent: A line that touches the circle at exactly one point.

2. Tangent Properties

• The tangent at any point of a circle is perpendicular to the radius through the point of contact.
• The lengths of tangents drawn from an external point to a circle are equal.

3. Chords and Angles

• Equal chords of a circle subtend equal angles at the center.
• The perpendicular from the center of a circle to a chord bisects the chord.
• Angles in the same segment of a circle are equal.
• Angle in a semi-circle is a right angle (90°).