单选题
The outline of a sign for an ice-cream store is made by placing
of the circumference of a circle with radius 2 feet on top of an isosceles triangle with height 5 feet, as shown above. What is the perimeter, in feet, of the sign?
The outline of a sign for an ice-cream store is made by placing
of the circumference of a circle with radius 2 feet on top of an isosceles triangle with height 5 feet, as shown above. What is the perimeter, in feet, of the sign?
【正确答案】
B
【答案解析】[解析] 该题的关键是求等腰三角形的腰长。如图中所示做辅助线，根据题意可知，等腰三角形的那一条边所对的圆的圆心角等于90°，所以等腰三角形的底边长为[*]。再运用勾股定理可求得等腰三角形的腰长的平方为52+[*]=27，所以腰长为[*]。由上分析可得该牌子的周长为：
[*]
[*]