Math question: In a circle with center O, chord AB is parallel to the tangent CD at point C. If angle ACB measures 70 degrees, find angle AOB, in degrees.
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What is the cosine of an angle in a right-angled triangle given that the adjacent side is 5 units and the hypotenuse is 13 units?
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Math question: What is the limit as x approaches 2 of (3x - 7)?