試題詳解

65. The radius of the inscribed circle of a regular triangle is 1. There is a small circle of which two tangents to this circle and the two sides of the triangle take place at the same time, as shown in the figure. The radius of the small circle is
(A) 1 3
(B) 1 2
(C) 3 6
(D) 3 1 2 −