题干
如图，正方形CDEF的顶点D，E在半圆O的直径上，顶点C，F在半圆上，连接AC，BC，则
=____．
| B |
| C |
| A |
| C |
答案(点此获取答案解析）
| 5 |
| + |
| 1 |
| 2 |
| B |
| C |
| A |
| C |
| 5 |
| + |
| 1 |
| 2 |
