单选题
In the figure below, if the radius of circle O is 10, what is the length of diagonal AC of rectangle OABC?
【正确答案】
D
【答案解析】Use TACTIC 2. Trust the diagram: AC, which is clearly longer than OC, is approximately as long as radius OE.
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Therefore, AC must be about 10. Check: the choices. They are approximately 1.4, 3.1, 7, 10, and 14. The answer must be 10.
**The answer is 10. Use TACTIC 4: copy the diagram on your scrap paper and draw in diagonal OB.
[*]
Since the two diagonals of a rectangle are equal, and diagonal OB is a radius,
OA = OB = 10.
[*]
Therefore, AC must be about 10. Check: the choices. They are approximately 1.4, 3.1, 7, 10, and 14. The answer must be 10.
**The answer is 10. Use TACTIC 4: copy the diagram on your scrap paper and draw in diagonal OB.
[*]
Since the two diagonals of a rectangle are equal, and diagonal OB is a radius,
OA = OB = 10.