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If O is the center of the circle, them OTK is a right angle triangle.
THEREFORE, TK = = = = 80 units. ANSWER
Notice that 39 = 78/2 is the radius of the circle.
Solved.
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If you want to learn more about tangent lines to circles, look into the lessons
- A tangent line to a circle is perpendicular to the radius drawn to the tangent point,
- Tangent segments to a circle from a point outside the circle,
in this site.