Tangent lines and tangents to a circle
Overview
Important
A tangent to a circle is a line that intersects the circle at exactly one point. At the point of tangency, the tangent is perpendicular to the radius drawn to that point.
Important properties
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A tangent touches the circle at only one point.
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The tangent is perpendicular to the radius at the point of tangency.
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From a point outside the circle, exactly two tangents can be drawn to the circle.
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The lengths of the two tangents from a common external point to the circle are equal.