Math question: In a circle, if an angle at the circumference is twice the size of an angle at the center, what is the measure of the angle at the center?
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What is the area of a triangle with a base length of 6 units and a height of 9 units?
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Math Question: Find the derivative of the function f(x) = β«(x^3 + 2x) dx from x = 1 to x = 3.