There is a park near my house. It's very big and beautiful. It's fine today. I am in the park now. There is a book shop on my left. Some people are reading books. On my right, there is a long river. There are many flowers and trees near the river. There are some boats on the river. Some children are rowing boats. There is a hill in the park. I'm going to climb the hill. I like the park very much.

如图，一艘核潜艇在海面DF下600米A点处测得俯角为30°正前方的海底C点处有黑匣子，继续在同一深度直线航行1464米到B点处测得正前方C点处的俯角为45°．求海底C点处距离海面DF的深度（结果精确到个位，参考数据： $\sqrt{2}$ ≈1.414， $\sqrt{3}$ ≈1.732， $\sqrt{5}$ ≈2.236）

宗法制将“国”与“家”结合在一起，其结合点主要是