Find the common radian measure of an angle formed by a straight line passing through the center of a circle, with an arc length equal to half the circumference of the circle.
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Math Question: Find the 3rd derivative of f(x) = 2x^5 - 3x^3 + 4x^2 - 7x + 1.
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What is the measure of the angle subtended by a diameter in a circle?