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geometry intermediate
Problem
What is the slope of the line that is tangent to a circle at point (5,5) if the center of the circle is (3,2)? Express your answer as a common fraction.
Solution
If a line can be drawn tangent to a circle a the point , then it must be possible to draw a radius from the center of the circle to the point . This radius will have a slope of: A key fact to remember is that tangents to a circle at a certain point are perpendicular to radii drawn from the center of the circle to that point. This diagram summarizes that fact: Therefore, the slope of the tangent will be the negative inverse of the slope of the radius, which is equal to .
Final answer
-\frac{2}{3}