What is the value of the cosine function at 30 degrees on the unit circle?
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What is the equation of the quadratic function represented by the graph below? f(x) = ax² + bx + c, with vertex (2, -3), passing through points (-1, 8) and (5, -7).
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What is the average (mean) of the following set: 5, 8, 12, 15, 20?