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 AXB is
(A) (2πr)/3
(B) (4πr)/3
(C) (3πr)/2
(D) (πr^2)/3
(E) (2πr^2)/3
Explanation
An equilateral triangle has three equal sides, so the lengths of the three arcs must be equal, and thus each arc is 1/3 of the circumference of the circle. The circumference of the circle is 2πr, so the length of arc A X B is 1/3 of 2πr, or (2πr)/3.
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(编辑:马菲)