Students learn the following theorems related to tangents. If a line is tangent to a circle, then the line is perpendicular to the radius at the point of tangency. If a line is perpendicular to a radius at its outer endpoint, then the line is tangent to the circle. If two tangent segments are drawn to a circle from an external point, then the tangent segments are congruent. Students are then asked to use these theorems to find missing segment lengths and missing angle measures in given figures. Students also learn the definitions of common internal tangents and common external tangents.



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