Math question: In a triangle ABC, if angle B = 90 degrees, and circle O with center C and radius r is inscribed in the triangle, what is the length of AB?
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Math question: Find the slope-intercept equation of a line passing through (3, 5) and (2, 9).
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Math question: What is the 5th derivative of f(x) = sin(3x) + cos(2x)?