graph TD
A[角的度量] --> B[角度]
A --> C[弧度]
B -- "360° = 一圈" --> B
C -- "2π = 一圈" --> C
B <--> |转换关系| C
D[π] --> |关键转换: π rad = 180°| B
D --> |关键转换: π rad = 180°| C
E[单位圆] --> |半径 = 1| C
E --> F[三角函数]
F --> |sin, cos, tan 等| G[圆周运动]
F --> |sin, cos, tan 等| H[周期性变化]
style A fill:#f9f,stroke:#333,stroke-width:4px
style B fill:#bbf,stroke:#f66,stroke-width:2px
style C fill:#bfb,stroke:#f66,stroke-width:2px
style D fill:#fbf,stroke:#f66,stroke-width:2px
style E fill:#bff,stroke:#f66,stroke-width:2px
style F fill:#ffb,stroke:#f66,stroke-width:2px