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SAT官方每日一题:2011年10月16日

2012-03-04来源:互联网

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  2011年10月16日

  考试类型:Mathematics > Standard Multiple Choice

  Read the following SAT test question and then click on a button to select your answer. 

  In the figure above, inscribed triangle A B C is equilateral. If the radius of the circle is r, then the length of arc A X B is

  A. (2 times pi times r) over 3

  B. (4 times pi times r) over 3

  C. (3 times pi times r) over 2

  D. (pi times r^2) over 3

  E. (2 times pi times r^2) over 3

 

正确答案:A

解析:

An equilateral triangle has three equal sides, so the lengths of the three arcs must be equal, and thus each arc is 1 over 3 of the circumference of the circle. The circumference of the circle is 2 times pi times r, so the length of arc AXB is 1 over 3 of 2 times pi times r, or (2 times pi times r) over 3.