```python
import matplotlib.pyplot as plt
import numpy as np

# 构建数据
x = np.linspace(-2*np.pi, 2*np.pi, 50)
y1 = np.sin(x)
y2 = np.cos(x)

# 绘制图像
plt.plot(x, y1, label="sin(x)")
plt.plot(x, y2, color="red", linestyle="--", label="cos(x)")

# 添加图例
plt.legend()

# 添加描述信息
plt.xlabel("X")
plt.ylabel("Y")
plt.title("Sin & Cos Function")

# 显示图像
plt.show()
```