Important Concepts and Formulas
1. Secant: A line which intersects the circle
at two distinct points is called a secant of the circle.
2. Tangent: A line which touches the circle at
only one point is called a tangent. The tangent to a circle is a special case
of the secant, when two end points of its corresponding chord coincide.
3. Theorem 1: The tangent at any point of a circle is perpendicular to the
radius through the point of contact.
4. The length of the segment of the tangent from the external
point P and the point of contact with the circle is called the length of the
tangent from the point P to the circle.
5. Theorem 2: The lengths of
tangents drawn from an external point to a circle are equal.
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